ESCALANTE, Utah (AP) _ A couple missing since Sunday were found alive Tuesday at the wreckage of their single-engine plane on a mountain, authorities said.

The pilot, Bronson Rumsey, and his wife, Diana, both of Aspen, Colo., were found at the 10,100-foot level of Griffin Top where Rumsey had belly-landed the plane after his fuel pump malfunctioned.

''I suspected we had a frozen fuel pump or fuel line that prevented power from getting to the engine,'' Rumsey said. ''I picked the best place to put down - in a long field with 4-foot snow.''

''We were very lucky,'' Mrs. Rumsey added from her Garfield Memorial Hospital room in Panguitch, where she and her husband were in satisfactory condition, being treated for frostbitten feet.

''It's quite flat'' on Griffin Top, said Danny Perkins, a sheriff's dispatcher. ''There are steep canyons on both sides.''

He said the couple was found about 5:50 a.m. Tuesday. They were equipped with warm clothing and sustained the frostbite trying to walk to civilization.

Rumsey said he and his wife had only street shoes and returned to the plane Monday morning after covering about eight miles.

Back at the plane, they discovered the aircraft's emergency locater signal had not been set off and they manually activated it. However, authorities said they never detected the signal and found the plane by radar.

''Tuesday morning at 4 a.m. we were cuddled up in the airplane trying to keep warm and we saw the search and rescue units,'' Rumsey said. ''We turned on our landing lights to guide them.

''We were damn glad to see them and they were darn glad to see us unhurt and smiling at them,'' he added.

Civil Air Patrol crews from four states had launched a search for the Cessna 210 Centurion after it was reported overdue on a flight from Las Vegas, Nev., to Aspen. The plane left Las Vegas shortly after noon Sunday, said Bob Smith, flight operations officer with the Utah CAP.

The pilot filed no flight plan and had no radio contact with air traffic controllers, Smith said.

''CAP search and rescue experts worked much of the night with FAA officials from Salt Lake and Los Angeles flight control centers tracing radar tracks which led search teams almost directly to the crash site,'' Smith said.

''They had seen where they dropped off Las Vegas radar,'' he said.