CHICAGO (CBS)– Officials said a fire at mosque on the city’s south side was arson.

The fire started just after 6 p.m. Wednesday and caused serious damage to the interior of the Masjid Al-Farooq mosque, at 8950 S. Stony Island Ave. in Calumet Heights.

Police said it appears the fire was started by a boy who was participating in an after-school youth program.

The fire was being investigated as arson on Thursday, but so far, no one has been arrested.