Smoke from a failed vacuum pump, used to power medical tools, was the cause of yesterday's partial evacuation of Epsom Hospital, it has emerged.

Epsom firefighters were called to the hospital, in Dorking Road, Epsom, at 10.30am yesterday, June 10, after fire alarms went off inside the building.

As the cause of the problem was being investigated, outpatients in the affected areas, including the maternity unit and Bradbury wing, were evacuated, although no inpatients - those needing to stay in a bed - left the building.

Firemen located the problem in the hospital's boiler room and normal service resumed as normal at 11.50am, after they had left the hospital.

A spokeswoman for Epsom and St Helier hospital trust said the fire alarms were triggered by smoke in the boiler room "accidentally re-entering the hospital".

She said: "The smoke was caused by a mechanical failure in a vacuum pump which powers the suction tools our doctors and nurses use when treating patients. 

"The pump is housed within the hospital’s boiler room.  This smoke should have gone through the vacuum pump’s exhaust on the roof, but was blown back into part of the hospital’s roof by the wind.

"Because we have a contingency plan for every system in our hospitals, from the lighting to the monitors in the intensive care units, the suction tools were unaffected by the mechanical failure."

An Epsom fire officer said they found the "loft space about the Casey ward smoke-logged" when they arrived.

He said: "One of the generators in the boiler room was burning oil which was giving off smoke, which was going into the exhaust pipes and going into the loft space.

"We turned the generator off and the smoke stopped, so we knew it was the problem."

Dr Ruth Charlton, joint medical director of the trust, said: "I’d like to apologise for any inconvenience caused to our patients and their visitors during the evacuation.   

"I’d also like to thank the fire brigade for their speedy response and our own staff for their calm handling of the situation."