ACT Fire and Rescue has responded to a gas leak at the ANU School of Medicine at the Canberra Hospital on Gilmore Crescent in Garran.
Building four and five were evacuated as a precaution while firefighters investigated the leak.
Approximately 300 people were evacuated before firefighters gave the all-clear for students and residents to return to the area around 1.50pm.
The leak was isolated and firefighters conducted air monitoring operations to ensure the area was safe for staff to return.
Three fire pumpers, a hazardous materials unit, a breathing apparatus van and two commanders were tasked to the job.
The leak was first reported to authorities at 12.52pm and firefighters arrived at the hospital shortly before 1pm.
The gas line was ruptured by workers in the area.
No injuries were reported.