The U.S. military said a helicopter flying over the U.S.-Mexico border in Texas crashed on Friday, killing two National Guard soldiers and one Border Patrol agent, and injuring another soldier who was on board.

The UH-72 Lakota helicopter was assigned to a federal government's border security mission when it crashed near the city of Rio Grande, according to a statement from the Northern Joint Task Force. The cause is still under investigation.

The incident occurred on Friday afternoon while the helicopter was conducting aerial operations, the statement said.

Star County Judge Eloy Vera, the county's highest official, said those on board were one woman and three men. He added that the injured individual was in critical condition, and the names of the dead were not immediately released.

General Daniel Hokanson, chief of the National Guard Bureau, sent his condolences on the social media site X to the families, loved ones, friends, and colleagues of the three people who were killed, and offered prayers for the speedy recovery of the injured soldier.

Hokanson’s post said: "We mourn these tragic deaths." "It is a devastating loss beyond words. All of these individuals represent dedicated service and the best of America."

Border Patrol spokespeople did not immediately respond to messages seeking comment.

The crash site is located in the Rio Grande Valley in Texas, and the county mayor’s office posted on Facebook on Friday that it was assisting at a “helicopter crash incident” on the eastern side of the county.

Vera said the sheriff’s office secured the crash site and that federal officials were en route.

The border area is subject to intensive patrols by state and federal authorities, including routine aerial surveillance.

In January, a Texas Department of Public Safety helicopter conducting a patrol on the state border with Mexico lost power and crashed, according to officials at the time. The co-pilot suffered minor hand injuries, and the helicopter was severely damaged.

That helicopter was flying as part of Operation Lone Star, a border mission by Texas Governor Greg Abbott worth nearly $10 billion, which tests federal government authority to control illegal immigration.