MANY more people could have been killed if the explosion had happened a few minutes earlier, emergency workers said last night.

It emerged that a group of pensioners had been standing in the market place only ten minutes before the incident, waiting to board a coach for a trip to Dover.

Fire station manager Tony John said: "If it had happened later or on a normal working day, there would certainly have been multiple fatalities."

Police said the investigation was ongoing and that they still did not know what had caused the cylinders to explode.

Mr Herd was a welder who worked at an industrial estate on the outskirts of Durham City.

His wife of four years, Jennifer, is expecting their first child.

Last night, her mother said: "My daughter is absolutely distraught."

Steve Wharton, station manager of Durham Fire Headquarters, was one of the first firefighters on the scene.

He said: "When we first arrived, the van was a total fireball and our first priority was to tackle the blaze.

"It was very fortunate that this incident happened so early in the morning or else other people could have been harmed.

"Dozens of houses have been severely damaged and it is very lucky that no one else has been hurt.

"We are unsure of the cause at the moment, and investigations are taking place over the coming days."

Residents have been evacuated from their homes and are staying with family and friends until police confirm that it is safe to return.

Inspector Kevin Blakey, of Durham Police, said: "We had hoped to get residents back to their homes by Sunday, but things are taking longer than expected, so the re-opening of the area may take until Monday.

"The area will continue to be cordoned off while investigations are carried out, and residents from Front Street will only be able to return to their homes for essential items such as medication."

Despite the amount of debris, police cleared the surrounding roads, which were opened at 8pm last night.

Insp Blakey said: "We have had structural engineers at the area to make sure the buildings and their gas and electricity supplies are safe before the residents return to their homes."

John Watson, 83, whose home is in the market place, said: "The place is like a bombsite, there is stuff lying all over the place.

"The blast was absolutely enormous, it was just like an earthquake.

"After the first explosion, there were a further two smaller ones. One of them must have been the vehicle's fuel tank blowing up, it was terrifying."

Witnesses to the incident have been asked to call 01325-742549.