Cause of explosions may be difficult to determine

Britain: Assessment and demolition of dangerous structures at the oil depot rocked by blasts yesterday could take months, and the cause of the fire may be difficult to determine, safety experts said.

One expert expressed surprise that the substances stored at the depot - petrol, aviation gasoline and heavier oil products - were capable of causing such a massive explosion.

Dr Ivan Vince, safety, health and environmental specialist at ASK Consultants, said: "From what I have been able to find out about what is stored there - I can't understand what has caused this explosion."

The substances stored at the depot "should not have been capable of generating such a massive explosion in a storage depot", he said.

"I am sure there is a reasonable explanation. For example, if liquefied petroleum gas was stored there and a vessel exploded, that could cause an explosion of this magnitude."

Dr Vince said he did not believe there were any serious danger to the public as the smoke plume was buoyant and was being lifted high above the ground. It would mix with air and be greatly diluted before any of it came back down to the ground.

He said once the fire has burnt itself out, firefighters would move in quickly to douse it down.

"When the fire is dying, the smoke is less buoyant and so can cause a local hazard."

A highly-trained crew would make a detailed risk assessment before the site is made safe, and demolition crews would go in to remove dangerous structures. This could take months, he said.

Hertfordshire's chief fire officer Roy Wilsher said the damage at the Buncefield depot may mean no clues are left for the fire investigation team.

"It may well be that in terms of investigating the fire we are relying largely on witness statements gathered by the police."

A spokesman for the Health and Safety Executive said it was monitoring the explosions.

"We will be investigating the incident, but at the moment the emergency services are taking the lead. The site must be made safe before we can send our investigators in."

Mr Wilsher said 250,000 litres of foam concentrate were on their way to Hertfordshire from other parts of the country.

When mixed with water that would generate millions of tonnes of foam - enough to allow firefighters to begin tackling the blaze.

He said fire officers were in consultation with oil industry experts about the best way to tackle the flames.

Duncan Milligan, who lives near the scene of the blast and is press officer for the Fire Brigades Union, said: "There was an incident at Milford Haven some years ago and it burned for at least a week, and they needed to call on foam tenders from all over the UK."

He said in this instance the foam used was likely to be aqueous film-forming foam known as AFFF.

"Something else of critical importance is boundary cooling; cooling around the edges of the immediate area of flame and heat to stop it spreading," said Justin Balcombe, a disaster expert.

He expected the immediate vicinity of the blast to be shut for at least one week.

"The knock-on effect will be quite significant," he told Sky News. "It's a large industrial area with infrastructure in the area. The priority will be to establish control round the immediate area."

He said it was fortunate most buildings in the area were commercial properties which would have adequate insurance.

Meanwhile, road restrictions caused by the explosions led to travel chaos yesterday, with more disruption likely for today's morning rush-hour.

Sections of the M1 were closed, jams built up on adjoining roads and flights were delayed at Heathrow airport.

Some motorists failed to heed advice that there was no fuel supply problems, and there was evidence of panic-buying at service stations.

The police and motoring organisations warned motorists to avoid the Hemel Hempstead area.

The M1 was closed in both directions between junction 6 north of Watford, Hertfordshire, to junction 10 south of Luton. No traffic was being allowed to join the M1 southbound at junctions 11 and 12 northwest of Luton.

The short M10, which runs from junction 7 on the M1 to a point south of St Albans, was also shut.

Roads close to the scene of the blasts were also closed. These included the A4147, the A414 and the B487. All these roads link Hemel Hempstead with junction 8 on the M1.

The Highways Agency, which is responsible for England's motorways and major trunk roads, said: We are working very closely with the police and fire service in order to continue to assess the situation, and taking their advice on the duration of the motorway closures.

"Drivers should continue to listen to the news and travel bulletins, and bear in mind that because of the severity of the incident these motorway closures could continue into Monday morning."

Flights at Luton airport, the nearest major airport to the blast scene, were able to carry on normally.

However, at Heathrow there were some delays as the plume of smoke caused the closure of one of the four air routes into the airport.

To add to Heathrow's problems, thick early-morning fog resulted in some flight cancellations. - (PA)