The Billings Fire Department responded to a building fire alarm late Friday night at the Montana State University Billings campus.
Battalion Chief Boyd Vopel said once campus police arrived at the education building, where the alarm sounded just before 11 p.m., there were no visible flames or smoke.
Firefighter Gregg Dillon said burning plastic could be smelled, but the fire crew couldn't find the source.
The small room, he said, had a computer that wasn't hot and a space heater that wasn't in use.
"It's very strange," Dillon said. "But we reset the alarm, and it didn't detect smoke again."
Vopel said campus police would continue to monitor the building throughout the night.