Texas officials say a helicopter carrying three National Guard members and a Border Patrol agent crashed along the US-Mexico border, killing three on Friday.

Starr County judge Eloy Vera said a fourth person was critical in the wake of the crash, with the aircraft coming down in Starr County, near the town of La Grulla.

He added that the local sheriff had secured the site, and federal officials were coming to the scene.

The Starr County Sheriff’s Office confirmed on social media that it was assisting with a “downed helicopter incident”.

Texas Department of Public Safety lieutenant Christopher Olivarez said the crash occurred near La Grulla but did not provide further details.

He instead referred questions to the US Customs and Border Protection agency.

In January, a Texas Department of Public Safety helicopter patrolling the state’s border with Mexico lost power and crashed.

The co-pilot suffered a minor hand injury, and the helicopter was significantly damaged.

That helicopter was flying as part of Operation Lone Star, Texas governor Greg Abbott’s nearly 10 billion dollar (£7.7 billion) border mission that has tested the federal government’s authority over immigration.

Border patrol spokespersons did not immediately return messages seeking comment.