Investigators have ruled that the cause of a fire that destroyed an auto parts complex in Scarborough was accidental.

Chief Michael Thurlow of the Scarborough Fire Department said the state fire marshals have concluded their investigation into the fire that completely destroyed Scarborough Auto Parts on Holmes Road Aug. 21.

“There wasn’t enough evidence to put your finger on an exact cause,” said Thurlow, though investigators believed the fire began in a garage in back of the offices. Fire marshals think the fire could have started in one of the bays where a car was being disassembled. Thurlow said it was possible that something overheated and sparked the fire.

No one was in the building when the fire was first noticed around 9 p.m., said Thurlow, and no one was injured.

“The fire had a head start,” Thurlow said, adding that several things made it hard to save the building.

“We had three strikes against us from the very beginning,” he said. The fire had such a head start because the building was built before sprinkler systems and fire alarms were required. Also, Thurlow said the complex was about a mile away from the nearest water source.

Compressed gas and air bags stored in the building were continuously exploding as well, said Thurlow, making it dangerous to send in firefighters. “At that point we went into a defensive mode,” he said. “It was a very dangerous fire.”