(CNN) -- Emergency responders searched a mountainous section of Idaho Monday for a single-engine plane carrying five family members that went missing Sunday afternoon.
The pilot reported engine failure at 9,000 feet at about 3 p.m. MT (5 p.m. ET) and asked the Salt Lake tower for coordinates to a remote airstrip near Cascade, a small town in central Idaho, said Lt. Dan Smith of the Valley County Sheriff's Office in Cascade.
The plane dropped off the radar and all contact was lost, Smith said.
The unidentified family was heading from Baker, Oregon, to Butte, Montana, in a single-engine Beechcraft Bonanza aircraft.
Smith said authorities used the pilot's cell phone signal to narrow the search to a two- to- four-square-mile area in the mountains.
The Idaho Army National Guard is searching with two helicopters. Deputies and rescue workers also joined the search in mixed rain, snow and fairly high winds, Smith said.