Nampa firefighters are investigating the cause of a fire that broke out about 3 p.m. Friday in an unoccupied portable building next to Reagan Elementary School.

School officials said the smoke appeared to come from an area near a heating unit in the portable building. No one was injured.

Students and staff heard the fire alarm and followed fire evacuation procedures, then noticed smoke coming from the portable building, Nampa School District spokeswoman Allison Westfall said. The Nampa Fire Department responded to the scene and extinguished the fire in about 45 minutes.

Firefighters inspected the main school building before letting students go back in. School dismissed at 3:30 p.m., and fire officials helped divert vehicles from the fire scene.