The fire was reported at the Claremont Middle School gymnasium, located at 5750 College Ave., at about 1:30 a.m., fire Battalion Chief Eleanor Bolin-Chew said.
It was brought under control around 2:10 a.m.
Firefighters contained the fire to the roof, where it appeared to have started, Bolin-Chew said.
She said the fire does not appear suspicious but that investigators are looking into the cause.
