BELFAST – A sack of foam exercise mats erupted in flames in the Belfast Area High School exercise room Monday, filling the immediate area with smoke and causing the school to be evacuated.

“It was definitely intentional,” said Police Chief Allen Weaver. “Those mats just don’t start by themselves.”

Although fire damage was minimal and confined to the second-floor exercise room, smoke and water damage could total more than $100,000, Weaver said.

Monday’s fire was the third at the high school in the past year and is being investigated by the State Fire Marshal’s Office.

Last April a fire was set in a boys restroom at the high school.

A 15-year-old boy was charged with setting that fire but was found not guilty when tried as a juvenile. In May, a fire was set to some trash and drama props kept backstage at the high school gymnasium. That arson has yet to be solved. There was an alleged arson at the Waldo Regional Vocational Center that same month that has never been solved.

Kenneth Grimes, a fire marshal’s investigator, declined to speculate whether Monday’s fire was connected to the earlier fires. Grimes added that anyone “can draw conclusions. Anybody who knows there were three fires is going to draw a conclusion.”

Grimes said investigators had not determined the agent used to start the fire. He said investigators would compare the results of this fire with information gathered from the other fires. He urged anyone who might come across information about the fire to contact the authorities.

The fire set off the school’s sprinkler system. Besides flooding the exercise room and the second-floor hallway, the migration of that water to the floor below damaged first-floor ceiling tiles, overhead light fixtures and electrical wiring.

The water damage could have been more extensive but school custodians and firefighters managed to build a makeshift dam outside the gymnasium and prevent its floor from being flooded.

The exercise room overlooks the school’s swimming pool, which was being used by a kayak class at the time. The kayakers were evacuated in their swimming clothes when smoke from the fire wafted into the pool area.

Most of the students and teachers left their winter coats and personal belongings behind when they left the school. There were no injuries.

The fire was reported at 10:22 a.m. by Belfast police Officer Brian Cunningham. Cunningham was in the school on another matter and sounded the alarm when he heard the sprinkler system activate. School Principal Ron Gleason and teacher Hal Halliday attempted to tackle the blaze with fire extinguishers but were driven back by the smoke.

“It was real heavy, bad smoke. So thick you can’t see,” fire Chief James Richards said. “It had to be a hot fire for a few minutes to set off the sprinkler. Luckily, one of them was right above the mats.”

Besides ruining the exercise mats, the fire also destroyed two $3,000 balance beams used for gymnastics. Firefighters pulled some of the mats from the building and left the charred remains of others at the point of the fire’s origin to assist the State Fire Marshal’s Office.

Richards said 14 firefighters responded to the alarm and the fire was extinguished within minutes of their arrival. The firefighters entered the smoky building wearing air packs and exhausted the air supply of a dozen tanks. Fans were set up to push the smoke outside.

Morrill fire Chief Jethro Pease arrived with extra fans to help move the smoke.

SAD 34 Assistant Superintendent Paul Luttrell said the fire forced cancellation of today’s classes, although the weather likely would have done so as well. He said the district planned to have the school ready for classes Wednesday. A cleaning firm arrived at the school during the afternoon to begin freeing the building of smoke residue and soot.