LONDON, Dec. 11 (Xinhuanet) -- The explosions that hit Britain's major oil depot north of London on early Sunday was an accident, and police have confirmed casualties.

    Though the exact number of casualties had not been given, police did confirm there were casualties.

    Residents have been required to close up their windows and doors in fear of any danger from the heavy smoke.

    The blast, which happened at about 6:00 am local time (0600 GMT), sent heavy smoke up into the sky, darkening the early morning like sunset.

    Several residents living nearby said their houses have either the roofs blown off or tiles shaken down.

    One resident told BBC that he had heard an aircraft flied low in the sky right before the blast, but police later said they had not found any indication of aircraft near the explosion site.

    The oil depot, not far from Heathrow Airport, is a major one in Britain, storing fuels of BP, Shell, Texaco and some other small oil companies. Enditem