A fire broke out in the early hours of Monday in an apartment building in Dagenham, east London, forcing the evacuation of over 100 people.

London Fire Commissioner Andy Roe said on Monday that the London Fire Brigade (LFB) had declared a major incident, which would allow them to focus its resources on the fire.

The incident occurred at 2:44 a.m (3:00 UTC), while many residents were sleeping. By around 7:30 am, heavy smoke was still emanating from the structure and local residents were advised to keep windows and doors closed.

Some 40 fire engines and 225 firefighters tackled the fire at the building, which engulfed both residential and commercial units. But the cause of the fire is still unknown.

'Significant search and rescue operation' underway

"The building has a number of fire safety issues known to London Fire Brigade," Roe said.

"A full simultaneous evacuation of the building was immediately carried out and a significant search and rescue operation is under way," he added.

The London Ambulance Service said four people were injured and treated at the scene, while two others were take to the hospital.

"The brigade has stood up full strategic arrangements to deal with the incident and a rest center has been set up at Beacontree Health and Leisure Centre," LFB said, in the aftermath of the evacuation.

Local Member of Parliament Margaret Mullane credited the swift response of the emergency services for the blaze resulting only in "minimal" injuries. 

London Fire Brigade has announced that all residents of the building have been accounted for.

jcg/wd (dpa, AFP)