Two Rock Springs, Wyo., area men were in critical condition Friday in Salt Lake City after being burned Thursday in an explosion and flash fire at an oil well servicing equipment site near Coalville, Utah.

Johnny Russell, 34, suffered mostly third-degree burns over 71 percent of his body, and Harold Townsend, 40, suffered mostly second-degree burns over 55 percent of his body, a University Hospital nursing supervisor said.The men, who were flown to the hospital about 11:30 a.m. Thursday, are employees of Updike Brothers Inc., Newcastle, Wyo.

Doug McVey, administrator, Utah Division of the Occupational Safety and Health Administration, said Friday the accident occurred when the injured men were cleaning out the casing on an oil well preparatory to shutting it down.

He said the men were putting salt water into the casing when some kind of flammable mixture got into the water as it went through the pump system and tank.

"There was a flash at the pump. We haven't figured out where the flammable mixture originated, but we do know the fire occurred at the pump. It was more of a flash, not a sustained burning. There was no fire at the wellhead," McVey said.

He said the investigation is continuing to try to isolate the source of fumes or vapors. Wayne Clegg, a safety and health officer, is investigating the accident.

Ralph O. Updike, company vice president, who who was contacted early Friday in Rock Springs before heading to the accident site, said he had no information on the explosion and fire.

A Summit County sheriff's dispatcher, who was on an ambulance crew dispatched to the scene, said the site is about 15 miles northeast of Coalville in the Chalk Creek area. The North Summit Fire Department was called to the scene.