University of Minnesota students, faculty and staff evacuated the Mechanical Engineering building on Church Street Southeast because of a suspected gas leak late Monday afternoon.
University spokesman Matt Hodson said responders searched the building for a leak but found none and cleared the building for re-entry around 5:30 p.m.
University and Minneapolis police responded to a call from a professor after a graduate student reported hearing a hissing noise.
Officials evacuated the building around 4:20 p.m. By that time, seven fire trucks, two University police squad cars and four other emergency vehicles were on the scene.
Alexi Gusso and Marion Renault contributed to this report.