Workers take a break from deploying large buoys to be used as a border barrier along the banks of the Rio Grande on July 12 in Eagle Pass, Texas. Eric Gay/Associated Press

AUSTIN, Texas — The Justice Department has told Texas that a floating barrier of wrecking ball-sized buoys the state put on the Rio Grande violates federal law and raises humanitarian concerns for migrants crossing into the U.S. from Mexico.

President Biden’s administration told Republican Gov. Greg Abbott that the barrier installed this month near the border town of Eagle Pass, Texas, was “unlawful” in a letter dated Thursday and obtained by The Associated Press.

“The floating barrier poses a risk to navigation, as well as public safety, in the Rio Grande River, and it presents humanitarian concerns,” reads the letter, which also informs the state that the Justice Department intends to sue if the barriers are not removed.

Abbott’s office did not respond to a request for comment Friday, but on Twitter, the governor wrote that Texas was acting within its rights.

“Texas has the sovereign authority to defend our border,” Abbott tweeted.

The buoys are the latest escalation of Abbott’s multibillion-dollar operation to secure the state’s 1,200-mile border with Mexico. Other measures have included razor-wire fencing and arresting migrants on trespassing charges. The mission known as Operation Lone Star came under new scrutiny after a trooper said migrants had been denied water and that orders were given to push asylum-seekers back into the Rio Grande.

The Texas Department of Public Safety said this week that the trooper’s accounts, which were made in an email to a supervisor, are under internal investigation.

The buoy barrier covers 1,000 feet of the middle of the Rio Grande, with anchors in the riverbed.

Eagle Pass is part of a Border Patrol sector that has seen the second-highest number of migrant crossings this fiscal year with about 270,000 encounters – though that is lower than it was at this time last year.

The Biden administration has said illegal border crossings have declined significantly since new immigration rules took effect in May as pandemic-related asylum restrictions expired.