Three University of Colorado Boulder campus buildings were temporarily evacuated Wednesday morning after Boulder Fire-Rescue responded to a fire alarm.

Boulder Fire-Rescue responded to the alarm at around 8:30 a.m. Wednesday at the Muenzinger building at 18th Street and Colorado Avenue, according to CU Boulder alerts. Upon arrival, crews entered the building, evacuated everyone inside and began investigating light haze seen on the lower levels. Crews saw haze in the building but there was no active fire. The Muenzinger, Gold Biosciences and Porter buildings were evacuated since the three buildings are connected.

By 11:30 a.m. Boulder Fire-Rescue cleared the scene and turned the buildings back over to CU Boulder. No injuries were reported, according to a release. Boulder Fire-Rescue crews were unable to locate the direct cause of the haze within the building but attributed it to likely being a mechanical malfunction.

The buildings reopened as of 11:30 a.m. and classes in the buildings operated normally for the rest of the day. Muenzinger is CU Boulder’s psychology building located off Colorado Avenue and adjacent to Folsom Field. Gold Biosciences is the home of the molecular, cellular and developmental biology department and the Porter Biosciences serves the same department with special facilities including a two-story laboratory.

Buff Buses that were temporarily re-routed to avoid the area during Boulder Fire-Rescue’s response have since returned to normal routes.

It was a 2-alarm call, meaning that departments outside the city were called in to assist. Louisville Fire and Mountain View Fire Rescue aided at the scene.