The University of Arizona Police Department responded to a report of a fire from the Science and Engineering Library Friday morning.
Upon arrival officers found smoke and flames coming from inside a restroom on the second floor of the building, and assisted in evacuating the building.
Tucson Fire Department crews were able to extinguish the fire and keep it contained.
TFD Fire investigators determined a toilet paper roll dispenser was ignited and suspect arson was the cause.
UAPD say there are no suspects at this time.
The building will remain closed to the public as crews work to clean and repair damages.
Anyone with information about the incident is asked to call the non-emergency number at 520-621-8273 or the tipline at 520-621-8477.