More than 400 people were evacuated from Auckland City Hospital on Thursday after a nurse noticed a leak from a huge oxygen tank in the day-stay oncology unit.
The tank provides oxygen for most of the hospital. A spokesperson says a safety valve popped, indicating the tank's pressure was too high, so a nurse alerted the Fire Service.
Auckland District Health Board general manager of operations Ngaire Buchanan says 12 patients and more than 400 non-clinical staff were evacuated as a precaution.
No one was injured in the incident and an investigation has been launched.