At a news conference in Kalispell on Thursday, Chuck Curry, an undersheriff in charge of the department's search and rescue, said he had carefully looked for signs of survivors.
"There were no footprints leaving the site, no piled rocks, no written message -- nothing indicating anyone had survived or left the area," he said, according to the Associated Press.
Wreckage of the plane from which the survivors emerged in Montana.
(Flathead County Sheriff's Office)
One other passenger on the plane, Ken Good, 58, a Forest Service worker from near Kalispell, may also have survived the impact of the crash. He apparently managed to get out of the wreckage but died a few feet away.
There were three unbuckled seat belts at the site crash, and "now I know why," Dupont said.
The sheriff said he began to examine seats on the plane Wednesday afternoon, after getting the call that there were two survivors. He said it took two-and-a-half 2 1/2 hours of digging through the crash site before he could find the unbuckled seat belts.
"I have never seen an aircraft burned that badly," the sheriff said. "I don't know how they could have survived the initial impact. In a very short distance, the plane went from a very fast speed to stop."
The plane left Glacier Park International Airport on Monday afternoon on a planned 30-minute flight into the Flathead National Forest, according to the Forest Service. Those on board were supposed to conduct a plant survey and repair telephone equipment.
Bad weather interfered with an air search Monday, and the crash site was not found until Tuesday, when the sheriff announced that one intact body had been found and the other four appeared to have been badly burned.
According to the Daily Interlake, grieving family and friends were being briefed Wednesday by the Forest Service when news came that there were survivors.
"When the call came, and I learned there were survivors, I thought that there is just no way," the sheriff said. "It was astonishing to me. It still is. If there is a definition of 'miracle,' this is it."