Officials at the Health Sciences Centre say 50 gallons of formalin, a liquid similar to formaldehyde, spilled on the fourth floor of the Thorlakson Building on Thursday.
The entire building was evacuated, ambulances were redirected to other hospitals and a handful of elective surgeries were cancelled.
The Winnipeg Health Authority says cleanup has been completed and all floors have been declared safe.
It says there were slightly longer waits in emergency due to the disruption of lab services.
The leak was caused by a construction worker who accidentally broke a feeder pipe.
He was the only person directly exposed to the formalin, and was treated and allowed to go home.