Army investigators on Saturday headed to the site where a military helicopter crashed in southern Texas the previous day, killing two National Guard soldiers and a Border Patrol agent.

A third National Guard soldier in the helicopter was seriously injured, according to Gen. Daniel R. Hokanson, the chief of the National Guard Bureau. The names of those onboard may be released on Sunday, the National Guard said.

The personnel were on a flight that was considered a routine mission near Rio Grande City supporting federal border operations, according to Joint Task Force North, the unit of the U.S. Defense Department that works with federal law enforcement agencies on the border.

The crash, which occurred in La Grulla, a small city of roughly 1,400 people in Starr County about 110 miles west of South Padre Island, was unrelated to Operation Lone Star, the border program led by the state of Texas.

The flight was “providing monitoring and detecting capabilities along that sector of the border,” Maj. Ryan Wierzbicki, a spokesman for Joint Task Force North, said by email. All three people killed had been deployed to the Southwest border since October, he said, adding that no one on the ground where the helicopter crashed was injured.

In a brief video of the scene obtained by Reuters, a smoldering heap of twisted metal is shown in an open field under an overcast sky, as what appears to be emergency workers run toward the aircraft.