The cause of the fire that damaged an Albert Lea classroom Thursday evening has been confirmed as arson.

Albert Lea fire investigator Doug Johnson said the fire originated on a desk in a Lakeview Elementary fourth-grade classroom, located on the lower level of the school.

Officials do not know what was used to start the fire. Samples from the scene are being tested in a lab for accelerants.

Authorities were alerted to the fire at about 11:15 p.m. Thursday by fire alarms. While the fire was contained to a 5-foot-by-5-foot space, sprinklers caused water damage to nearby classrooms and hallways.

Arson hotline and arson reward posters have been hung up around the school. The Albert Lea Police Department is also investigating.

School administrators are hoping to resume class on Monday.