Aviation officials are still investigating the reason why a firefighting airplane from Missoula, Mont., crashed unexpectedly near Stockton Pass Saturday morning, killing all three occupants.

The Tooele County Sheriff’s Office was dispatched to Stockton after residents reported hearing a low-flying airplane and then a crash just after 10 a.m.

“They said the crash sounded like two semis hitting head on,” said Sheriff Frank Park.

An initial search of the area — conducted by Tooele County Search and Rescue, who was participating in training exercises at Five Mile Pass when the call came in — was hampered by low clouds and rain.

“Visibility was down to 150 feet,” Park said. “The clouds were low, right down to the highway. We couldn’t see anything at all, so we were scouring to find anything.”

Tooele County dispatchers contacted the Salt Lake International Airport to inquire whether a plane was down in the area, but the airport wasn’t able to confirm anything, according to Park.

“We continued looking and then a little after 11 a.m. the Salt Lake Airport called back saying there was a plane traveling from Missoula, Mont., to Alamogordo, N.M., that was missing,” Park said.

The National Interagency Coordination Center in Boise, Idaho, was tracking the airplane, which was en route to help douse a 19,000-acre wildfire in New Mexico.

“Their last contact was just south of the Erda airport,” Park said. “So at that time we were positive we had a plane on the mountain.”

Still visibility presented a problem in locating the wreckage.

“We could barely see across the highway,” Park said. “Search and Rescue members were driving ATVs all over the foothills just looking for anything.”

At 1 p.m., searchers located the wreckage 1 mile east of milepost 49 on SR-36.

“Then the clouds lifted and the whole county could see the wreckage from the highway,” Park said. “I would say it was no more than 1,500 to 2,000 feet from the road. Had the plane been an eighth of a mile to the west it would have gone over the Stockton Bar and been fine.”

Park said the wreckage was spread out over approximately 100 yards on the steep terrain of the Oquirrh foothills.

“When a plane hits going this fast into the hill it disintegrates,” he added. “There are a lot of small pieces around. There are several larger pieces — wings, tail sections, fuselage — but the rest is just scattered around the mountain.”

The plane’s crew — pilot Tom Risk, 66, of Littleton, Colo., Mike Flynn, 59, of Alamogordo, N.M., and Brian Buss, 32, of Alberton, Mont. — were killed on impact. Deputies and search and rescue members transported the bodies off the mountain Saturday evening.

“Our immediate concern was the bodies,” Park said. “The occupants were definitely dead on impact. Our lack of being able to find the wreckage, though frustrating, had no effect on life safety. Once we had the bodies out and there was no danger of fire, we turned the scene over to the National Transportation Safety Board and the Federal Aviation Administration.”

The plane — a P2V Neptune, which was developed during the Korean War — is a large aircraft with two prop engines and two jet engines, according to Park.

“It’s a very good aircraft capable of flying through all kinds of inclement weather,” he said, adding that both Risk and Flynn were very experienced pilots.

The NTSB, which has been working the crash site since Sunday, is following up on leads from witnesses and scouring wreckage to help determine what caused the crash.

“We’ve had reports from people in Grantsville that they had seen this same plane circling around Grantsville at a low altitude,” Park said. “NTSB is the investigating agency at this point.”

According to Peter Knudson, spokesperson for the NTSB, fatal aviation investigations usually take about 12 months to finalize.

“We usually see the preliminary report within 10 days,” Knudson said. “Then somewhere between six and 10 months later we see the factual report, and then finally a probable cause report.”

Jamie Belnap: jamieb@tooeletranscript.com