A major search and rescue operation continues at the site of the Francis Scott Key Bridge in Baltimore after it was struck by a cargo ship and collapsed early Tuesday, sending cars plunging into the water below. The U.S. Coast Guard said the ship had reported losing propulsion and control as it was leaving Baltimore harbor, before the collision occurred at around 1:30 a.m. ET. 

Two people were pulled from the water overnight, officials said — one unhurt and one with serious injuries. 

Maryland Department of Transportation Secretary Paul Wiedefeld said at a mid-morning news conference that rescue teams were still looking for six people unaccounted for after the bridge collapse. He said all six were part of a construction crew that was filling potholes on the bridge at the time.

Maryland Gov. Wes Moore declared a state of emergency, with city, state and federal teams converging at the scene. 

Map of the Key Bridge in Baltimore

The Key Bridge crosses the Patapsco River, a key waterway that along with the Port of Baltimore serves as a hub for East Coast shipping. CBS News Baltimore station WJZ reports that the four-lane, 1.6-mile span was used by some 31,000 people a day.

The Maryland Transportation Authority said all lanes were closed in both directions on I-695, which crosses the Key Bridge. The agency said traffic was being detoured to I-95 and I-895. 

The portion of the bridge that collapsed was on a stretch connecting Hawkins Point, on the south side of the waterway, and Dundalk, on the north. 

Video of the Key Bridge collapse in Baltimore

Video captured the moment the heavily loaded container ship struck a bridge support, sending sections of the overpass tumbling into the river below.

The ship — the Singapore-flagged Dali — was operated by charter vessel company Synergy Group and was chartered by Maersk, carrying Maersk customers' cargo, the companies said. 

Officials said in a news conference that a mayday had been issued before the collision, which allowed officials to stop traffic onto the bridge. Officials did not clarify how many vehicles were on the bridge at the time of the collapse. 

Moore said he "can confirm that the crew notified authorities of a power issue," and he said that the decision to stop traffic onto the bridge "saved lives last night." 

Earlier Tuesday morning, Baltimore Mayor Brandon Scott called the collapse "an unthinkable tragedy."

"We have to first and foremost pray for all of those who are impacted, those families, pray for our first responders and thank them," he said. "We have to be thinking about the families and people impacted. We have to try to find them safe."

Follow the latest on this developing story from CBS Baltimore.

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