State officials say they have a good idea what caused the three-mile stretch of fires that broke out along railroad tracks in Old Orchard Beach and parts of Saco and Scarborough last week, but they are not yet ready to release their findings.

The fires destroyed sections of the Wagon Wheel RV Resort and Campground in Old Orchard Beach, including 10 seasonal trailers and several propane tanks. The fires damaged seven other trailers.

The damage was exacerbated because the campground was just opening for the season and many of the propane tanks used by summer vacationers had recently been filled.

The fires caused $250,000 in damage at the campground, fire officials said. The estimate will allow owners of the trailers to file insurance claims.

The persistent fires drew 75 firefighters from 20 communities.

The fires erupted just as a freight train passed. Some residents reported seeing sparks coming from beneath the train as it passed. Pan Am Railways owns the freight train and the track.

A Pan Am Railways spokeswoman said the train was inspected when it reached its destination in Dover, New Hampshire, and there was no sign that it was responsible for the fires.

Railroad officials said last week that the inspection showed that the engines’ exhaust was clean and the brakes showed no signs of any malfunction.

The Maine Forest Service is in charge of investigating the cause of the fires. Identifying who is at fault could influence liability and regulatory issues.

John Bott, spokesman for the forest service, said Friday that while the investigation is almost done, the results are not ready to be released because there are still some details that must be incorporated.

“We’ll have something to say in the near future,” he said.

The results will identify who is at fault for the fires, including whether the freight train was responsible and how.

“We want to be absolutely sure. That’s why we want the few remaining pieces of information,” Bott said.

David Hench can be contacted at 791-6327 or at:

dhench@pressherald.com

Twitter: @Mainehenchman