All four crew members aboard a military helicopter that crashed at Fort Hood in Texas Monday afternoon were killed, the U.S. Army said.

The crew's UH-60 chopper went down some time after 5:49 p.m. in the northeast portion of the Fort Hood Range, according a statement released by the Army.

Emergency crews found the wreckage after an extensive search.

The members of the Division West, First Army were on a routine training mission at the time, the Army said.

The cause of the crash was under investigation.

The Army said it would not release the names of the victims until 24 hours after next of kin could be notified.

It was the second fatal crash involving a U.S. Army helicopter on Monday. Both pilots aboard an Apache were killed after it came down 50 miles east of an American base in South Korea.