Four people died in the crash of a small plane Friday morning in a rugged area in the Utah mountains, authorities said.

Utah County Sheriff’s Sgt. Spencer Cannon confirmed, via Twitter, that the pilot and three passengers were on board when the crash occurred, in the Box Elder Peak area in American Fork Canyon. The pilot was Tyson Colby Brummett, 35, of Salt Lake City. His passengers were Alex Blackhurst Ruegner, 35, of Riverton and Alex’s aunt and uncle: Elaine W. Blackhurst, 60, and her husband, Douglas Robinson Blackhurst, 62, both of Riverton. All four died on scene.

The canyon is about 35 miles southeast of Salt Lake City.

The single-engine plane took off from South Valley Regional Airport in West Jordan. The crash took place just before 8 a.m.

The cause of the crash is not yet known. Cannon said he believed the plane was on an “up-and-back” flight through the valley.

The Associated Press contributed to this report.