OLD ORCHARD BEACH — Forest rangers used a helicopter Thursday to dump water on a brush fire that started along railroad tracks and spread through a campground, causing explosions and destroying a number of campers.

Dozens of firefighters from as far away as Windham and Gorham assisted the local fire department in dousing the flames. There were no reports of serious injuries.

Steve Berard, who restores cars at a business in Old Orchard Beach, said he watched the flames spread from the brush alongside the railroad tracks to the Wagon Wheel RV Resort and Campground, which is behind the shop where he works. Explosions sent flames shooting 20 feet into the sky, causing flames to spread, he said.

“The campers went in a domino effect because of the propane bottles. Every time they exploded, they caught the next one on fire,” Berard said.

Firefighters blamed sparks from a train for setting a series of brush fires. Grass and vegetation along the railroad tracks were extremely dry.

The operator of Amtrak’s Downeaster said the passenger train was not responsible for the flames. The train passed through Old Orchard Beach around 1 p.m., but was not connected to the fires, an official said. Pan-Am Railways was investigating whether a freight train was to blame.

Old Orchard Beach Fire Chief John Glass said firefighters were getting the blaze under control by early evening. Firefighters remained on the scene.