The body of a man who drowned in the Rio Grande was found Wednesday in the floating barrier of buoys installed by the state of Texas to deter migrant crossings from Mexico, officials said.

It was not immediately clear how the man, who was not identified, ended up in the barrier, which runs for roughly 1,000 feet in the middle of the river by the small border city of Eagle Pass, Texas. Mexican officials said in a statement that they had been alerted by the Texas state police around 2:35 p.m. that the body had been discovered “caught in the southern part of the buoys.”

Officials from the Texas Department of Public Safety, whose officers patrol the banks of the river around the barrier, said the man appeared to have drowned farther up the river and then floated down.

“Preliminary information suggests this individual drowned upstream from the marine barrier and floated into the buoys,” Steve McCraw, the director of the Department of Public Safety, said. “There are personnel posted at the marine barrier at all times in case any migrants try to cross.”

A spokesman for the department said that the body was found on the Mexican side of the barrier and that Mexican officials had recovered it.

The Mexican government has objected to the placement of the buoys in the river, which were installed without federal approval last month by Gov. Greg Abbott of Texas as part of his multibillion-dollar program to use state law enforcement to deter illegal crossings from Mexico.

“The placement of chained buoys by Texas authorities is a violation of our sovereignty,” the Mexican Foreign Ministry wrote in its statement on the drowning. “We express our concern about the impact on the human rights and personal safety of migrants of these state policies.”

Under another part of Mr. Abbott’s program, known as Operation Lone Star, migrants who make it across the river and onto private land in Texas have been arrested and charged with criminal trespassing by the state police.

Officers in recent weeks have begun arresting some men who were traveling with their children, separating them from women and children, who were sent to Customs and Border Protection for processing.

Previously, the state had refrained from arresting any member of migrant families if the children were under 18 years old.

“In the past, they didn’t want to break up family units,” said Kristin Etter, a lawyer with Texas RioGrande Legal Aid who represents migrants charged with trespassing under Operation Lone Star. “The policy change is to now arrest the father and separate the family.”

“We’re aware of 26,” she said of the number of men separated from their families. “But I’m sure there are a lot more out there. That’s just clients that we know of.”

State police officials acknowledged some instances in which fathers were separated from their children, but said children in those cases remained with their mothers and were turned over to the Border Patrol. The change was reported in The Houston Chronicle.

Many of the recent trespassing arrests in Eagle Pass have taken place on city-owned land in Shelby Park, Ms. Etter said, after the mayor gave state police permission to close the park and make arrests there.

But in a sign of local displeasure with the closure of the park and the harsh tactics employed by the state against migrants in recent months, the Eagle Pass City Council voted unanimously on Tuesday to revoke that permission.

Despite objections from immigrant rights advocates as well as Democrats in Texas and in Washington, the Biden administration has mostly avoided a direct confrontation with Mr. Abbott over his stepped-up actions at the border, which began after President Biden took office.

But after the installation of the buoy barrier, the federal government filed suit, arguing that the barrier in the Rio Grande violated federal law and had prompted diplomatic protests by Mexico. It has asked a court to force Mr. Abbott to remove the buoys, arguing that they create additional dangers for migrants seeking to cross the Rio Grande, whose fluctuating waters have been responsible for dozens of migrant drownings in recent years.

Border Patrol officials in the area of Eagle Pass have complained that steps taken by Mr. Abbott, including the installation of the buoy barriers and the unfurling of miles of concertina wire along the riverbank, have made it more difficult for border agents to assist migrants in distress.

A ruling in the federal lawsuit was expected as early as next week.

Local officials had remarked on the relative lack of reported drownings in the last two weeks.

Though there had been some reports that two bodies had been found near the barrier, the Department of Public Safety spokesman, Travis Considine, said the body in the buoy barrier was the only one found in the river by Texas state police on Wednesday.

Mexican officials said that on Wednesday they found the body of a second man who had drowned in the river, a few miles from the barrier.

René Martinez, a rescuer with Grupos Beta, which helps migrants in crisis, appeared to have been one of the first to encounter the body near the buoy barrier on Wednesday.

He said he had responded to a call and found the body of what appeared to be an adult male just inches away from the barrier; the man appeared to have been dead for some time, he said.

“It wasn’t stuck to the buoys, but the remains were pretty close to it,” he said. He said he called Mexican authorities, who came to investigate and remove the body.

Two hours earlier, he said, he had been called to the scene of another body by the river, most likely the one reported by Mexican authorities, about three miles from the buoys, on the Mexican side of the river. He said that the body appeared to belong to an adult male who also died some time ago.

“It is lamentable to see these situations. These are things that should not happen but happen,” Mr. Martinez said.

Valeria Wheeler, the executive director of Mission: Border Hope, a respite center in Eagle Pass, says that drownings are a common cause of death among people attempting to cross the Rio Grande. She often hears from migrants who arrive at the center and tell harrowing stories of having watched others drown, she said.

“That’s something that happens very often, even before those measures were put in place,” Ms. Wheeler said, referring to the buoys and razor wire installed by Texas. “It’s awful.”