CORONADO, Calif. -- A fire that started in the bleachers of the Coronado High School's gymnasium Sunday and triggered automatic sprinklers may have caused more than $500,000 in damages because of a possibly destroyed wooden gymnasium floor, a Coronado fire captain said.

The incident was reported at 8:20 a.m. Sunday as a smoke alarm. Firefighters, stationed less than a block away from the high school, were in the gym quickly and were able to extinguish the blaze in 20 minutes, said Capt. Jim Blinn.

Maintenance workers had been in the process of resurfacing the floor, he said, and the fire did not appear to be intentionally set. The gym was locked when firefighters arrived, he said.

Damage was confined to the gymnasium building, and was caused mainly by smoke and water. Blinn estimated damages starting at $250,000, which could double depending on whether professionals can save the floor.

"If they have to replace the gym floor, it could be a half-million dollars," he said.

An investigation as to how the fire started, and if woodworking chemicals were involved, continues, Blinn said.