At least 4 injured as explosion rocks London apartment block (PHOTOS, VIDEO)

Homes in a borough of London have been evacuated after an explosion tore through a block of flats.

Four people are being treated for injuries sustained in an explosion on Monday evening, according to the London Ambulance Service. 

Police say the incident occurred just after 5pm on the Ardleigh Green Road, in Hornchurch in East London. 

The exact cause of the explosion or the extent of the damage is not yet known and emergency services are reportedly still at the scene.

Reports suggest that explosion may have been caused by a propane canister, although there has been no official confirmation.

“At this early stage officers are unable to confirm the cause of the explosion but enquiries are underway,” a Metropolitan police statement said.

“Residents are in the process of being evacuated from the building. The local authority has been informed and also on the scene.”

Amateur video footage from the scene show at least five fire engines and numerous ambulance vehicles attending the incident.

Road closures are in place and people are being asked to avoid the area.