Amherst, NY – AMHERST, N.Y. — Four people have been treated at a hospital after a dormitory at the University at Buffalo was evacuated for a carbon monoxide leak.

University spokesman Joe Brennan tells media outlets that an equipment malfunction near the boiler room caused the deadly, odorless gas to build up inside the building Sunday evening. Campus police started getting calls around 8:30 p.m. for students feeling nauseated and headachy.

He said two students drove to a hospital and two others were taken to a hospital by ambulance. Two students were evaluated by an ambulance crew at the scene.

Brennan says firefighters shut off the faulty boiler quickly and ventilated the building. Students who had been evacuated to other buildings were allowed to return several hours later.