Two members of the New York State National Guard were identified as victims in a military helicopter crash that killed three people in Texas on Friday near the U.S.-Mexico border.

John M. Grassia III, a New York State trooper, and Casey Frankoski, a National Guard helicopter pilot, were killed near La Grulla, Texas, when the chopper crashed into a field. Chris Luna, a U.S. Border Patrol agent, also died in the crash, according to the Department of Homeland Security.

All three had been deployed along the southern U.S. border since October.

The death of Mr. Grassia, 30, was announced by the New York State troopers union in a social media post, which said he had joined the force as a state trooper in 2022. Ms. Frankoski was named in a Facebook post by the mayor of her hometown, Rensselaer, N.Y., where her father is a retired police chief.

The operation last week was said to be a “routine mission” along the U.S.-Mexico border, where Mr. Grassia, Ms. Frankoski, and two others were working with Joint Task Force North, a U.S. Defense Department initiative that tracks the boundary along with local and federal law enforcement.

The group had been “providing monitoring and detecting capabilities along that sector of the border,” said Maj. Ryan Wierzbicki, a spokesman for the task force.

The helicopter was following people who were illegally crossing into the United States when it crashed, according to Judge Eloy Vera, a top local official in Starr County, the site of the accident.

Army investigators arrived at the site this weekend and were expected to comb the wreckage for the black box of the aircraft, a UH-72 Lakota, used regularly in such missions by the Army as a light utility aircraft.

A third National Guardsman was seriously injured in the crash, the National Guard said.