A fire damaged a small portion of a mobile classroom unit last night outside Mark Twain School in Niles, school district officials said.
The fire started sometime after midnight on the northeast stairs of the mobile unit, according to an email alert sent from school Principal Nichole Gross to families.
No one was inside at the time and no one was injured, said Scott Clay, superintendent of East Maine School District 63.
Clay said the mobile unit sits between the playground and school building in the 9400 block of North Hamlin Avenue.
The stairs are not visible to motorists or residents, Clay said, and have been the site of increased evidence of loitering.
The district has seen a recent spike in graffiti on the mobile unit, which houses two classrooms Clay said are used to house after-school program activities.
According to Clay, the district is examining camera systems for installation near the mobile unit.
"It shouldn't take long once we figure out the right system to use," he said.
Clay said the fire appears to have started when someone set fire to a plastic bottle, which burned a hole through one of the wooden steps and spread to a 4-foot by 8-foot section of siding.
The step and siding section must be replaced, Clay said, but no other portion of the unit's exterior or interior sustained damaged.
He said the district has worked with police to increase patrols in the area.
Niles police were not available for immediate comment.