(CNN) — The Justice Department told Texas Thursday that it intends to file legal action against the placement of floating barriers in the Rio Grande as part of the state’s operation along the Texas-Mexico border, according to sources familiar and a letter obtained by CNN.

The Justice Department sent the letter to Texas Gov. Greg Abbott Thursday, according to the letter, though there is time for the state to respond.

“The State of Texas’s actions violate federal law, raise humanitarian concerns, present serious risks to public safety and the environment, and may interfere with the federal government’s ability to carry out its official duties,” the letter stated, citing a clause in the law that “prohibits the creation of any obstruction to the navigable capacity of waters of the United States, and further prohibits building any structure in such waters without authorization from the United States Army Corps of Engineers (“Corps”).”

This is separate from the ongoing assessment of mistreatment of migrants, which the Justice Department described as “troubling reports.”

CNN reached out to Abbott’s office for comment. CNN has also reached out the Texas Department of Public Safety but has not received a response.

The Justice Department has sued on border-related matters before. Last year, the Justice Department sued Arizona for placing shipping containers along the US southern border – a move taken by then-Republican Gov. Doug Ducey as an affront to Biden’s immigration policies. Arizona eventually agreed to remove the containers.

The news comes as more than 80 Democratic US lawmakers sent a letter to President Joe Biden Friday urging him to investigate Abbott’s “dangerous and cruel actions” on the southern border after a Texas state trooper blew the whistle regarding alleged inhumane treatment of migrants and Mexico’s top diplomat complained to Washington about Texas breaking two international treaties.

“We write to express our profound alarm over border policies instituted by Texas Governor Greg Abbott that are putting asylum-seekers at serious risk of injury and death, interfering with federal immigration enforcement, infringing on private property rights, and violating U.S. treaty commitments with Mexico,” the letter states.

The inspector general for the Texas Department of Public Safety has received several additional complaints from DPS personnel on the front lines at the border about the treatment of migrants trying to enter the United States, three sources familiar with the investigation told CNN. Among the complaints are reports that Texas troopers were told to push back migrants into the Rio Grande and ordered not to give them water.

In a Tuesday joint statement with other Texas top officials, including Department of Public Safety Chief Steve McCraw, Abbott’s office said there have been no orders or directions given under Operation Lone Star that “would compromise the lives of those attempting to cross the border illegally.”

The effort, led by Rep. Joaquin Castro, also includes more traditionally conservative Democrats like Rep. Henry Cuellar.

The authors of the letter highlight that Abbott’s border initiative, known as Operation Lone Star, and says Abbott’s actions have “escalated in recent months,” detailing “sharp razor wire” in the Rio Grande, which is “creating death traps for migrants and violating U.S. treaty commitments with Mexico.”

“The placement of razor wire and inflatable buoys in the Rio Grande River is potentially illegal and may violate multiple bilateral treaties between the United States and Mexico, including the Boundary Treaty of 1970 and the Mexican Water Treaty of 1944,” the letter states. “A similar attempt to create a makeshift border by Governor Ducey in Arizona was abandoned earlier this year after Department of Justice filed suit against the State of Arizona.”

The letter goes on to say that Abbott’s border initiative policies “pose a huge danger to migrants” and urges Biden to take action and “stop this horrific abuse of power.”

Biden administration officials have grown increasingly concerned over recent months about Abbott’s measures along the Texas-Mexico border.

“It’s making our job harder,” one Homeland Security official told CNN.

In a significant development Wednesday that was first reported by CNN, the Justice Department said it’s assessing the situation along the Texas-Mexico border – marking an escalation from an administration that for months had stopped short of taking any actions against Texas.

“The department is aware of the troubling reports, and we are working with DHS and other relevant agencies to assess the situation,” DOJ spokeswoman Xochitl Hinojosa told CNN on Wednesday.

An administration official said Abbott’s actions “are preventing Border Patrol agents from accessing the river, patrolling the area, and arresting individuals who attempt to enter the country unlawfully,” adding that agents have also had to cut through multiple layers of concertina wire to respond to medical emergencies.

This story has been updated with additional reporting.

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