PATIENTS and staff at a Blackburn hospital had to be evacuated after a chemical leak.

The chemical alert was sparked after a dangerous substance leaked out of a pipe and into a store room at the Hill View unit run by Lancashire Care NHS Trust last night.

At around 7pm firefighters from Blackburn and Darwen were called after reports of a hazardous material leak.

They said acid which had been used earlier to unblock some drains had leaked through a pipe into a ground floor store room.

It produced fumes which effected the electrics causing some of the lights to trip out.

The area was cordoned off and staff and patients were evacuated to the second floor of the three-storey building. The exact number of people affected is not known.

Firefighters wearing specialist gas suits and officers from the Hazardous Material Unit in Burnley entered the room and started to remove some of the contaminated material.

Damian Hartley, watch manager at Blackburn fire station, said: “We carried out an investigation and found that an acid which had been used to unblock a drain had corroded a pipe and leaked into a store room on the ground floor.

“The chemical was producing a bad smell and it had effected the electric fuse box which had tripped some of the lights out.”

Three fire engines were at the scene and the area remained cordoned off until 10.30pm.

Mr Hartley added: “It appears that some contractors used an industrial drain unblocker on site which has corroded the pipework and caused the leak.

“We sent in a specialist unit who removed all the contaminated boxes and material and disposed of it.”

A ventilation unit was also used to disperse the gas which had build up in the area.

Bosses at the hospital in Haslingden Road confirmed that a full investigation into the incident will now take place.

Declan Hadley, a spokesperson for Lancashire Care NHS Trust, said: "I can confirm that there was an incident at the hospital on Friday night.

"A smoke alram was triggered and the fire brigade was called out.

"Patients and staff were evacuated to an adjacent ward after a chemical reaction caused smoke to fill an area in the hospital "The chemical had been used to unblock a drain earlier in the day.

"Engineers are now investigating the cause of this incident."

Patients and staff have now returned to the L2 ward in the hospital.