(NEXSTAR) — A National Guard helicopter crashed near Texas’ border with Mexico on Friday afternoon, leaving at least two people dead, multiple law enforcement sources confirmed to Nexstar.

The helicopter went down in La Grulla, a small town in east Starr County on the Rio Grande River, Lt. Chris Olivarez with the Texas Department of Public Safety confirmed.

At least four people may be critically injured, DPS South Texas Regional Director Victor Escalon told Nexstar. Escalon could not independently confirm further information and directed inquiries to Customs and Border Protection.

Escalon said the helicopter was not a part of Operation Lone Star, Texas’ unilateral border enforcement arm utilizing the National Guard, but “a military helicopter on federal orders working with Border Patrol.”

DPS is assisting federal agencies with the response, according to KVEO.

This is a developing story. Check back for updates as more information becomes available.