British firefighters are mounting a massive operation using foam to smother a ferocious fire still raging at the nation’s fifth largest fuel depot. The blaze is the result of several explosions at the Buncefield depot, near Hemel Hempstead north of London, early on Sunday. Police say the blasts, which injured 43 people and blew out windows and doors from nearby houses, appeared to be an accident.The Chief Constable for Hertfordshire, Frank Whiteley, said on Monday: “During the day we hope to be able to escort a number of business owners onto the premises so they can start to make an assessment around security and getting their businesses back into operation.” Thick black smoke has been billowing out of the oil and petroleum depot and drifting over southeast England. The smoke cloud has already reached the northwestern French regions of Brittany and Normandy. It is expected to arrive in northern Spain by Wednesday. About 200 schools are shut today in the region surrounding the depot although some of the 2,000 people evacuated from their homes have returned.