The shocking collapse of Baltimore’s Francis Scott Key Bridge after it was hit by a cargo ship early Tuesday morning has the region reeling.

Thus far, two people who were working on the bridge have been rescued and six are presumed dead by their employer, Brawner Builders, given the temperature of the water and the time that has passed since the accident, the Associated Press reported Tuesday evening. Sonar, robots, and human divers were among the resources deployed in the Coast Guard’s search, which ended some 18 hours after the collapse. Two bodies were recovered Wednesday, but as of now the search for remains has been paused as divers can’t safely work around the debris from the bridge.

“This is an unthinkable tragedy,” Baltimore Mayor Brandon Scott said at a press conference on Tuesday morning.

The collapse of the bridge will also affect transportation in the region — and potentially global trade.

Used by 31,000 vehicles each day, the Key Bridge is a central conduit for traffic in the area. The incident also comes as the global shipping industry is facing several other challenges, including a record-breaking drought in Panama and Houthi strikes on ships in the Red Sea. Due to closures at the Port of Baltimore — one of the busiest in the country, especially for foreign cargo — logistics and shipping companies will likely need to reroute more key deliveries.

Authorities have acknowledged these concerns — and the challenges they pose — but emphasized that they’re secondary to the human lives affected.

Why did the Baltimore bridge collapse? What happened with the ship?

The incident took place around 1:30 am ET Tuesday when a large cargo ship called the Dali abruptly lost power and collided with a support column on the Key Bridge, a 1.6-mile structure that stretches across the Patapsco River.

After the ship — which holds a volume of 95,000 gross tons — hit the column, video shows parts of the four-lane bridge crumbling rapidly and collapsing into the water.

Shortly before the collision, the crew of the ship, which is owned by a Singaporean company called Grace Ocean, reported that they had lost control of the vessel and issued a “mayday” call. Dali was originally headed from Baltimore to Colombo, Sri Lanka, on behalf of Maersk, the major Danish shipping and logistics company.

As experts told USA Today, the bridge failure was so catastrophic because the ship took out a support column — a key component that kept it structurally sound — while going at a high speed. “Any bridge would have been in serious danger from a collision like this,” Nii Attoh-Okine, the chair of civil and environmental engineering at the University of Maryland, said.

For now, it’s not clear what caused the ship to lose power, though the National Transportation Safety Board (NTSB) is conducting an investigation. (Last June, an inspection in Chile found the Dali had some propulsion issues, but a standard US Coast Guard inspection later in the year found no problems.) Jennifer Homendy, the chair of the NTSB, said that agency investigators had boarded the ship overnight to collect data and will begin interviewing crew members Wednesday.

Authorities have also concluded that there’s no evidence this was an intentional incident or terrorist attack. “Everything so far indicates that this was a terrible accident. At this time we have no other indication,” President Joe Biden said Tuesday afternoon in a press conference.

What do we know about casualties from the Francis Key Bridge collapse?

When the collapse happened, a group of eight construction workers were filling in potholes on the bridge. Two of those workers have been rescued, including one who was in stable condition and one who was hospitalized.

The remains of the four other workers have not yet been found. They include people from Mexico, Guatemala, El Salvador, and Honduras, several outlets report. The identities of the workers have prompted some to question the risks they faced.

The tragedy, though, could have been far worse: thousands of vehicles cross the bridge each day on average. But immediately after the ship’s “mayday” call — and before it collided with the bridge — government officials were able to shut down additional vehicle traffic, preventing cars and passengers from being harmed. (Vehicles can be seen falling into the river in videos, but authorities said these were the parked cars of construction workers.)

“These people are heroes. They saved lives last night,” Maryland Gov. Wes Moore said at a press conference about the ship’s crew.

Are bridges safe? Has a cargo ship crashed into a bridge before?

Yes, bridges are safe — but not as safe as they could be.

In the 1970s, the Federal Highway Administration (FHWA) adopted the National Bridge Inspection Standards regulations, after a horrible 1967 accident in West Virginia where the Silver Bridge collapsed and killed 46 people. The accident ushered in a new era of bridge safety at the national level. In 2022, the FHWA updated its standards to incorporate recent technological advancements.

But not all bridges are created equally. One in three bridges in the US are in need of repair or replacement, according to the American Road and Transportation Builders Association. Maintenance helps bridges be able to withstand stressors such as natural disasters, for instance. The FHWA classifies bridges into three ratings: good, fair, and poor. Those with poor ratings are prioritized for repairs first.

To be clear, Key Bridge was structurally sound with a fair rating. It’s just not designed to absorb the shock of an incredibly large and heavy cargo ship ramming into it, engineers say. (As the Guardian’s Oliver Milman points out, current bridge code doesn’t account for today’s supersized cargo ships, some of which are far bigger than the Dali.)

Nonetheless, the National Transportation Safety Board, the federal agency responsible for investigating transportation accidents, will be looking deeper into the safety of the bridge.

“Part of our investigation will be how this bridge was constructed,” said Homendy during a NTSB press briefing Tuesday. She stressed it will take time, referencing the investigation for the 2022 Fern Hollow Bridge collapse in Pennsylvania, which took two years to fully complete.

When it comes to the cargo ships: It is not uncommon for a ship to lose power as the Dali did Tuesday, according to attorney Matt Shaffer, who handles maritime law cases, and without power, a ship of that size can cause extensive damage.

But cargo ships bumping into a bridge and causing it to collapse isn’t common. Since 1960, it’s happened just 35 times worldwide. As of 2015, a total of 342 people have died from bridge failures caused by ships. To put that in perspective, more than 40,000 people in the US died in a car accident in 2020, according to some estimates.

How important is the Francis Scott Key Bridge, and what’s next for it?

The Francis Scott Key Bridge — named after the poet who wrote the lyrics to what became the national anthem — not only connects commuters from one part of the harbor to another, it plays an important industrial role. It’s one of three major crossways for the Baltimore Harbor.

In 2023, more than 12.4 million passenger and commercial vehicles crossed the bridge, according to the Maryland Transportation Authority. Bloomberg News reported that it transports $28 billion in goods annually — with nearly 4,900 trucks crossing daily. The bridge and its almost nine miles worth of approaches serve as a final link in I-695. From there, the interstate connects the city’s port to I-95, the major highway along the East Coast.

Construction of the bridge started in 1972 and was completed March 1977. It cost $60.3 million at the time to build. The bridge is mostly made of lightweight concrete, according to a November 2021 report by the US Federal Highway Administration. Lightweight concrete, the report notes, isn’t typically used for bridge construction, but it “can be used as a durable and cost-effective material for bridges.”

Bridges are a feat of engineering — and are rightfully expensive. A $60 million project in the 1970s would cost far more to execute today, especially given increased scrutiny for speed and safety (and inflation). Rebuilding the bridge will likely cost “several billion dollars,” Yonah Freemark, a researcher at the Urban Institute, told Bloomberg.

Biden, during the press conference Tuesday afternoon, said that it is his “intention” that the federal government will pay for reconstructing the bridge. “And I expect Congress to support my effort,” he added.

Even with federal money, it could take months, if not years, to rebuild, disrupting both commercial and commuter traffic in the region.

What does this mean for the shipping industry?

The search and rescue operations have shut down the port of Baltimore, which has become an increasingly important shipping hub for the eastern US.

The port is the 17th largest in the nation based on the amount of cargo that goes through the port, and it handles the largest amount of transportation cargo — cars and trucks, but also coal, farm equipment, and construction machinery, the New York Times reported. Kevin Doell, Maersk’s North American media representative, told Vox that the Dali was carrying a “wide variety of cargo” from a number of different customers, but did not elaborate.

The broader economic impact will likely be limited — already, nearby ports like one in Virginia are talking about supporting temporary diversions. But the terminal’s closure could have regional effects, and it is another setback for the global shipping industry in an already difficult year.

Maersk, the company that chartered the Dali, said in January that it would no longer send its vessels through the Red Sea and Bab al-Mandeb strait near Yemen, where Houthi forces have targeted ships since November in response to the Israeli war in Gaza. Because of the risk of damage, injury, and kidnapping, some global shipping companies have opted to take the longer shipping route around the Horn of Africa, which can add as much as two weeks to a voyage and comes with attendant fuel and salary costs for the companies.

The Panama Canal, another global commercial transit hub, is also causing issues for the industry. A massive drought in Panama has severely limited the number of ships that can use the canal, slowing transit times and increasing costs.

Though the Baltimore port has played an increasing role in trade, it’s too soon to see what the commercial fallout will be. Other ports can absorb the container ships Baltimore would take — companies have the option to send their cargo to ports throughout the East Coast, including in New York and Virginia, industry executives told the Times.

But the damage will most likely be felt in the auto industry, given that Baltimore is the country’s largest auto importer. General Motors and Ford were already re-routing their vehicles and auto parts to Brunswick, Georgia, as of Tuesday; that could mean some supply chain delays, but any disruptions are expected to be minimal, according to a statement from GM.

Some companies may opt to send their goods to West Coast ports and then ship them east, rather than risk bottlenecks as eastern ports reorient their operations, Flexport CEO Ryan Petersen told Bloomberg. That was already going on prior to the accident, as 45,000 dockworkers with the International Longshoremen’s Association on the East and Gulf Coasts were threatening to strike should the union not reach a fair contract with ports and shipping companies by October 1.

Update, March 28, 12:15 pm ET: This story, originally published March 26, has been updated with further developments.

Clarification, March 28, 12:15 pm ET: This story has been changed to make it clearer that Maersk did not own the Dali, it chartered the ship.