SALT LAKE CITY — Maybe it was residual heat from a long-smoldering pile of burned logging debris.
Maybe it was a spark from an ATV.
Or maybe it was arson.
Those are all possible causes of the 7,211-acre Church Camp Fire, according to a state report issued Tuesday, more than five months after the fire began in Duchesne County.
"We wanted to take all the necessary time to make sure we got to the bottom of it, if there was a bottom to be found," said Jason Curry, spokesman for the state Division of Forestry, Fire and State Lands.
"In this case, it seems like nothing really was clear enough to be conclusive," he said. "Sometimes we just have to say, 'We don't know for sure.'"
The Church Camp Fire began June 24 in Argyle Canyon on property owned by the state School and Institutional Trust Lands Administration. It started near a slash pile — a mound of tree limbs and other plant debris that is discarded during logging operations. SITLA officials told fire investigators their records show the pile hadn't been burned since December 2010.
"I've seen slash piles hold over winter and over snowstorms before," Curry said. "But the (pile) that was burned in 2010, that would have meant that it had to hold over for well over a year.
"I've heard of documented cases where that has occurred," he added. "I don't know if the circumstances in this case were sufficient to allow it to hold over for that long. It doesn't seem to me or anybody else that that was very probable in this case."
Witnesses also told investigators that just before the first flames were spotted, a teenager was seen riding away from the area on a small ATV, according to the state report.
Authorities have not been able to identify the teen, the report states, or determine whether a spark from the ATV or the heat of its exhaust may have ignited the tinder-dry fuels on the ground.
They also haven't ruled out the possibility that the fire was intentionally set, said Curry, who was one of the investigators on the fire.
"We consider (arson) in nearly all the cases we investigate," he said.
The inability to identify who is responsible for the fire — based on the available evidence and witness statements — means taxpayers will foot the $5.7 million bill for fighting the Church Camp Fire. But Curry said the investigation can always be reopened, if new information comes to light.
"We are always open for further investigation if more leads become available or we determine there's more evidence," he said.