Two fire crews were called to a branch of Boots after blaze fears were triggered by a smoke bomb set off by a security system.

Ham & High: Smoke billows from the front of the pharmacy after the security device was set offSmoke billows from the front of the pharmacy after the security device was set off (Image: Archant)

Firefighters from West Hampstead raced to the pharmacy in Hampstead High Street, Hampstead Village, on Sunday morning after white smoke was seen billowing from the shop front.

They arrived at about 10am only to discover it was a false alarm, caused by a “smoke screen” security device that emits a dense white fog to deter burglars and obscure their vision.

The device was set off accidentally and then triggered a fire alarm, a staff member said.

“We have a smoke screen here, basically if anyone tries to come in, then smoke comes out,” she said.

“My colleague tried opening the shop up after we had a power cut and it just went off.

“There was no burglar, sometimes it just happens.”

She added that the devices are installed in all Boots branches, although this was not officially confirmed by the company when asked by the Ham&High.

Cllr Chris Knight, who represents Hampstead Town ward, praised the swift response of the fire service, but criticised the security arrangement that generated the false alarm.

He said: “They need to tie that up because it’s not the fire brigade’s job to tackle burglars.

“They have to link up the technology a bit better, so the security device doesn’t waste firefighters’ valuable time.

“But it’s a huge comfort to know they can be there so quickly.”

The London Fire Brigade did not want to comment on the potential for false alarms.

A Boots spokesman said: “We can confirm an incident took place at the Hampstead store on Sunday, before the store opened.

“There were no customers in the store at the time and the store traded as usual that day.

“We regret that the fire crew were called out and we are investigating the matter to avoid this happening again.”