The incident, at the institute based in Huye District, happened on Wednesday around 7:00am
The fire outbreak affected some rooms and damaged computers, tables, closets and examination papers among others.
According to PIASS Vice-rector in charge of Academics, Rev. Prof. Viateur Ndikumana, they suspect poor electrical installations to be behind the incident.
Rwanda National Police intervened to extinguish the fire before it spread further around the premises.