The construction of a private border wall partially funded by rightwing allies of Donald Trump continued with vigor in south Texas this week, seemingly in blatant violation of a court injunction ordering work to be suspended.

On Thursday and Friday, within three days of a temporary restraining order being issued, the Guardian found construction crews with at least 10 heavy machinery vehicles moving soil, digging trenches and positioning tall metal posts along the US bank of the Rio Grande in Hidalgo county, which forms the border with Mexico. A 3.5-mile, privately-funded concrete barrier is planned on the site, near Mission, Texas.

The state court order was served to We Build the Wall (WBTW), an anti-migrant group founded by military veteran Brian Kolfage, and the landowners, Neuhaus and Sons LLC, whose land is situated between Trump’s proposed wall and the Mexican border.

WBTW is a not-for-profit group that has crowd-funded millions of dollars by tapping into anti-migrant fervor and is led by former White House advisor Steve Bannon as chairman of its advisory board. Kolfage has described migrants as terrorists and drug traffickers, and accuses border wall critics as being cartel collaborators.

The injunction, issued on Tuesday by a state judge, was granted citing potential “imminent and irreparable damage” to the National Butterfly Center, a popular 100-acre riverfront nature reserve adjacent to the Neuhaus property. The wall could act as a dam and redirect floodwater and debris to the sanctuary, destroying an ecosystem which sustains hundreds of native butterfly species and birds, the center said.

Shortly after the ruling, Kolfage posted a video on Twitter of a man standing on the riverbank wearing a fluorescent vest, identified only as “Foreman Mike”, who said that thanks to “patriotic donors” a mile and a half of land had been cleared, and steel bollards and panels would be installed within 48 hours.

“We’re going to be putting this up,” said the foreman, Mike, asking for more donations, while promising to have the barrier built by mid-January 2020. “We have to supercharge it now. It’s time to get really moving.”

On Wednesday, Kolfage said that construction work continued as neither he, or the group, had been physically served with the order.

Work was still going on on Friday afternoon when the Guardian was given access to an adjacent private plot, and witnessed crews moving soil, excavating a trench on a vast stretch of cleared riverbank, and preparing it for concrete foundations and metal posts. A Border Patrol vehicle was parked close to the bulldozers, partially hidden by lofty sugar cane.

An employee of the construction company Fisher Industries, who identified himself as Sean, confirmed that work had continued uninterrupted – despite the injunction.

“They [the construction workers] have told us they are not going to stop,” Sam Pena from the local sheriff’s office said on Thursday. The sheriff’s deputies filed reports documenting the ongoing construction work that appeared to be in violation of the court order.

And, on December 5, the federal government launched separate legal action to stop the construction, on the grounds that it violated binational treaty obligations with Mexico. A temporary injunction was granted by the US District judge Randy Crane.

That federal lawsuit, filed on behalf of the International Boundary and Water Commission (IWBC), states that required hydraulic studies proving that the wall would not worsen flooding on the river had not been completed, and scant detail about the planned work had been submitted.

“At last the federal government is doing what it should be doing,” said Sarah Burt, a lawyer from EarthJustice, a not-for-profit legal group, which is suing the government over the border wall. “There is still a rule of law in this country, and everyone should be subject to it.”

But, in a twist, judge Crane agreed to dismiss WBTW as a defendant after its lawyer and prominent conservative, Kris Kobach, the former Kansas secretary of state, claimed the group mostly handled “social media cheerleading” for the project and was nothing more than a passive investor, providing only 5% of the funding.

“We don’t have any control over the project or the machinery or what’s going on,” Kobach said in court in the Southern District of Texas.

The removal of WBTW from the lawsuit raised questions about the group’s finances, which has attracted scrutiny from the authorities – and supporters who have donated at least $25m to build a wall.

“Where is the money?” said Javier Peña, a lawyer acting for the National Butterfly Center. “They use fear and anger to divide people and convince them to give money for a wall which they now say they are not funding. We build the Wall is either misleading its donors, which is fraud, or lying to a federal judge.”

Kolfage has said he aims to raise $1bn for his cause to boost the Trump administration’s push for a new barrier between the US and Mexico, which Trump has repeatedly promised, in vain,would be “paid for by Mexico”.

On its website, the group claims that Project 1, a wall stretching just under a mile long in New Mexico, has stopped “100% of illegal crossings”. The Hidalgo county stretch is known as Project 2, and “multiple [other] projects are underway”, Kolfage told the Guardian.

“We Build the Wall are investors in wall projects, we are not contractors nor are we builders. We fund walls and unite people to build border walls. There is no discrepancy, these walls would not be built without our funds,” said Kolfage.

Thursday’s federal injunction prevents Neuhaus and Sons, the landowners, Fisher Industries and its parent company, Fisher Sand and Gravel, from excavating and clearing more land, or constructing any permanent structures until the IBWC determines whether it could cause flooding or redirect the water flow in violation of the 1970 binational treaty.

The North Dakota-based Fisher companies are owned by Tommy Fisher, who has made regular appearances on Trump’s favorite TV channel, Fox News, to boast about how he could build the wall, faster, better and cheaper than anyone else.

Earlier this week, Fisher Sand and Gravel was awarded a $400m Pentagon contract to build 31 miles of wall in Arizona – despite a history of environmental and tax violations

The chair of the House Committee on Homeland Security, Bennie Thompson, has called for an investigation to determine whether Trump unduly influenced the military’s decision to award the contract to Fisher.

Multiple requests to Tommy Fisher for comment have not received a response.

The Trump administration has suspended 28 laws relating to clean water, public lands, endangered species and the rights of Native Americans in order to speed up construction of the border wall.

But such waivers only apply to the official government wall; rogue private projects must obey all laws and treaties.

The Texas lawsuit in which the butterfly center is a plaintiff also includes a defamation claim, because Kolfage has repeatedly accused Marianna Treviño-Wright, head of the butterfly center, of criminality.

Kolfage responded: “There’s no defamation. The open border policies of the butterfly people 100% enable the cartels and humanitarian crisis. No one crosses the border without paying the cartels.”