Just before 12:40 p.m. Tuesday, students and faculty members in the eastern side of the College of Arts and Sciences building, at 725 Commonwealth Avenue, were evacuated after a fire alarm went off.

According to Boston Fire Department Engine 33 firefighter Louis Priego, the department was notified by a master box alarm inside the building that went off at approximately 12:35 p.m.

“The master box went off and it sent it to the central station,” he said. “Then we received the call about 10 minutes ago.”

The fire department, Boston Police Department and the BU Police Department all sent units to the scene.

College of Engineering freshman Michael Bobbie said he was evacuated from the building during his Calculus II class.

“The alarm went off, and our teacher told us to go out the doors and to the right to exit the building,” he said.

Other students shared similar, uneventful stories, as everyone was evacuated safely.

Students who evacuated from the building were crowded onto the sidewalks of Commonwealth Avenue in front of the Tsai Performance Center and the side of the CAS building on Granby Street until 1 p.m., when they were allowed to re-enter the building.

Fire department officials said they did not know the cause of the alarm, however, the building was secure, and the situation was “nothing serious.”

“The smoke detector from the inside unit went off,” one official said. “It could be anything, but it was on the roof.”