About 50 people escaped unharmed when fire broke outyesterday around 2 p.m.

It is thought the fire was accidentally started by workmen using a blow torch to carry out repairs to the roof.

Thick black smoke and roaring flames coming from the side of the building alerted residents.

Former councillor Frank Wren, who was outside the building at the time, said: "People were still in the office so I called them to get out quickly. Those people were extremely lucky because they just weren't aware the fire was right above their heads."

Mohammed Aslam, of Hartington Street, was at home when he heard a small bang and saw a big cloud of smoke. "It was full of people on the streets, they all came running out. At first it was looking like it was all going to blow up, it was very dangerous."

Watch Manager at Burnley Fire Station Ian Potter said: "As far as we're aware it's a blow torch that has caused the fire. The fire was confined to the area on the top of the roof and we managed to stop it spreading.

"It's cosmetic damage more than anything with some water leakage and a couple of panes of glass have gone through inside."

Patients who use the centre and who need urgent appointments are being directed to Pendle Valley Surgery at Yarnspinners Health Centre, Nelson. All telephone calls to Brierfield Health Centre are now automatically diverted to the Pendle Valley Surgery, and NHS Direct has been notified.

Health staff are also working from the nearby Family Tree Centre in Brierfield for people who turn up for booked appointments at the health centre.

Anyone with an urgent problem during normal surgery hours should go to Burnley General Hospital's Urgent Care Centre up to 6-30 p.m. After that time the out of hours service is available by contacting the normal surgery telephone number.

A full assessment of the damage is being undertaken and the situation is to be reviewed.