Three crew members working on a reality television program died in a helicopter crash early Sunday morning. The names of the people involved have not been released. The Bell 206B Jet Ranger crashed while filming in Polsa Rosa Ranch in the city of Acton, a rural area of northern Los Angeles County.

According to a filming permit the show was a military themed program for Discovery.

Laurie Goldberg, a channel spokesperson said the show had not been announced yet. “A production company was shooting a show for Discovery Channel when this tragic accident occurred,” the channel said in a statement. “We are all cooperating fully with authorities. Our thoughts and prayers go out to the families.”

A spokesman for FilmLA, the company that processes film permits for location shoots in the LA area said that the production company had was approved to use a helicopter for a shoot that was taking place from Saturday afternoon until Sunday night.

The cause of the crash is still unknown and both the FAA and National Transportation Safety Board are currently investigating the situation.