LONDON and the South East will be shrouded in a toxic cloud of smoke for days, as firefighters struggle to contain the inferno still burning at one of Britain’s largest oil depots.

An investigation has begun into the causes of the blaze, which erupted shortly before dawn yesterday. Just after 6am, explosions ripped through fuel storage tanks at the Buncefield complex on the edge of Hemel Hempstead, Hertfordshire. As the inferno fed on the combustible cocktail of diesel, petrol and aviation fuel stored in container tanks and pipelines, more tanks detonated during the morning, sending flames leaping hundreds of feet. Last night a fire chief said that more explosions were still possible.

From dawn a plume of oily smoke could be seen pumping from the heart of the fire and drifting south and eastwards in an almost windless sky. Like an airborne oil slick, it hung low in the sky on an otherwise bright winter day, blotting out the sun and casting a grey pall over surrounding villages. The fumes tainted the air, catching the breath and stinging the throat.

Fire chiefs said that it was the largest such incident in Europe since 1945 and admitted that they were struggling to get enough chemical foam to suffocate the flames.No one died and most of those closest to the explosion escaped with minor injuries.

A worker at the depot was last night in intensive care at Watford General Hospital with lung injuries. Forty-one people were treated for various minor injuries and a man who had been at the depot was being kept in hospital for observation.

Had the disaster happened on a working day, hundreds of people would have been in the depot and the surrounding industrial estate.

The cost to the industry of yesterday’s blast could be up to £250 million according to experts. Hans Michels, Professor of Safety Engineering at Imperial College, London, said that each of the 20 tanks on the site was worth £10 million.

Terry Hines was one of five tanker drivers queuing for fuel at the site when he saw steam and vapour pouring from one of the tanks. “Suddenly all the electricity tripped out.” Mr Hines said. “A guy on the forecourt told us to get out as quickly as possible. We were walking away when there was a massive explosion. The air was sucked past us and there were pipes and things flying around. It threw us across the yard and we got up and ran to the gates, but they were locked. We had to clamber through the gaps to get out.”

Raheel Ashraf, a security guard, was on the top floor of a building next to the complex when he smelt fumes. “In seconds there was a humungous blast. I fell down and, when I opened my eyes again, there was nothing left of the building.

“It was a miracle I didn’t have a scratch. The building was torn apart and I was stuck on the top floor. Luckily there was a lot of rubble, blocks and concrete and I was able to jump down and crawl out.”

On Wellsbury Terrace, in Leverstock Green, half a mile across fields from the depot, almost every house had its windows broken by the blast. Police in facemasks went from door to door telling residents to evacuate their homes because of the danger of further explosions.

Andy Catling, 21, was woken by his bed rocking. “The whole house shook, I saw a big flash and all the car alarms went off at once outside,” Mr Catling, a student, said.

“There was a whooshing sound just beforehand, everyone came out on to the street. We are all in complete shock.” All perhaps except Bob Ashton, who slept through the drama and was woken at 9.25am by a friend checking to see that he was OK.

“The police want us to evacuate, but people are worried about leaving their homes unguarded,” Mr Ashton said.

The residents of one house had left their shattered front room full of shards of glass and ruined Christmas decorations.

Hilary Gaywood was walking around in her coat and pyjamas making sure relatives and friends were accounted for before she left her own home.Petrol stations in the area were closed to prevent panic buying and in a local DIY superstore customers bought out the stock of protective dust masks.

On every corner, people stood, stared at and photographed the column of smoke dominating their landscape. There were reports that the blasts were audible in France, Belgium and the Netherlands.

Police and fire chiefs ruled out rumours of an air accident or a terrorist incident but the exact cause of the fire remains unexplained. Bobby McQueen, who drives past the site each day, said he believed that there had been attempts to deal with a leak during the past week.

“I saw thick foam being applied close to one of the fences, it seemed they were trying to stem some sort of leakage,” Mr McQueen said.

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