FIRE crews were called to a hospital after cylinders began to overheat and threatened to leak potentially deadly chlorine gas.

Crews were called to Newcastle's Freeman Hospital when it was discovered a storeroom containing eight cylinders full of a sodium hypochlorite solution were overheating.

The cylinders were starting to swell in the heat and fire crews were brought in to release the pressure. They removed the cylinders to a secure compound where they could be safely dealt with.

A hospital spokesman said the incident, at 5.30am yesterday, happened in an external storeroom and no patients were affected.