More than 50 firefighters battled a string of stubborn brush fires that broke out along several miles of railroad tracks in Kingston, Newton and Plaistow yesterday afternoon.

The fires are believed to have started when a train passed through and sparks ignited the woods that line the tracks.

Fire officials and several neighbors who live along the tracks described the fire as the worst they've seen of its kind.

A command center was set up at the Newton Fire Department as fire crews from more than 15 agencies from across Rockingham County and northern Massachusetts moved in to help fight the fires that threatened homes in the area. The tracks were shut down for several hours as firefighters fought the flames, which spread quickly.

Firefighters said they had a tough time fighting the fires because of the extreme heat, dry conditions, and gusty winds that continued to fan the flames. The fires broke out around 2 p.m., and smoke could be seen for miles in either direction along the tracks.

Newton Fire Capt. Dale Putnam said one Newton firefighter was treated for heat exhaustion. Putnam said he didn't know whether the train that sparked the fires was an Amtrak passenger train or a freight train operated by Pan Am Railways.

The train was eventually stopped in Newfields to be inspected.

Newton resident Robert White, whose front yard borders the tracks, said he was outside spreading loam in his yard when he saw the train go through and then the brush and a utility pole along the front of his driveway went up in flames.

"This is definitely the worst," said White, who has lived at his Bartlett Street residence for 21 years.

Like other neighbors, White and his son, Kevin, 13, quickly grabbed a 400-foot hose and rushed over to attack the flames before they spread closer to his house.

The fire also spread to the Whispering Pines campground, which borders the track. Damage was confined to the area closest to the tracks.

A plane from the Civil Air Patrol eventually was brought in to search the area along the tracks.

Several neighbors helped firefighters as they searched for hot spots. Karen Finn used a stick to poke around the ground. "It just keeps starting back up," she said.

Jackie Leone, a resident of Laura Lane in Newton, said she became concerned when she saw her neighbor's backyard go up in flames.

This is the second time in as many weeks that a train is believed to have started brush fires. Several fires broke out in Kingston, East Kingston and Exeter on April 12. Fire officials said is appeared that those fires were caused by a train from Pan Am Railways.