JULIAN, Calif. -- The still-smoldering Volcan Mountain fire that destroyed 29 cabins or trailers at a hunting camp may not have been arson after all.

California Department of Forestry fire investigators told the San Diego Union-Tribune they have been unable to find any evidence to suggest a person deliberately started the Sept. 6 blaze, which charred 685 acres.

"We just don't know yet," CDF Battalion Chief Mike Neill told the newspaper. "Arson is possible, or possibly it was mechanical."

Initial reports of arson were based on witness seeing a motorcyclist speed away from the flashpoint in a canyon about 4 miles east of Farmer and Wynola roads.

The fire was contained Sept. 12 but, because large trees were burning, firefighters do not expect to declare the fire out until the end of the month.

The motorcycle's exhaust may have sparked the fire, Neill said.

No one was seriously injured in the fire, but most of the structures at the Volcan Mountain Hunter's Camp were destroyed.