A MASSIVE explosion rocked Trowbridge in the early hours of yesterday morning when Army bomb disposal experts blew up incendiary devices dating from the Second World War after they were dug up on a building site.

The Army team was called to the site in Wingfield Road on Wednesday evening to destroy the phosphorus explosives. They discovered far more explosives underground than first thought, which delayed the detonation.

At around 12.40am on Thursday, a controlled explosion was carried out in a skip after the devices had been carefully excavated from the ground and the road was back to normal before rush hour on Thursday morning.

Wingfield Road was closed off and a 100-metre area was cordoned off, causing traffic chaos as people tried to enter and leave the town after work.

Residents were told to stay inside and keep their windows and doors shut while parents and staff were evacuated from a parents’ evening at John of Gaunt School.

Firefighters who spent almost 12 hours on the operation said they are pleased with how smoothly it went and have thanked the community for their co-operation.

After being called out at around 4pm, they set to work on alerting residents in the cordoned off area to remain inside and it was not until 3.30am that they left the scene.

Damien Bence of Dorset and Wiltshire Fire Service, who was acting as the hazardous materials officer said: “We were called at around 4pm and arrived to make the scene was safe and try and identify what the devices were.

“It all went smoothly but it was a very long drawn-out process because the excavation took so long.

“A few of the bottles broke during the excavation which meant the boys from the Army had to cover the area back up with clay again and start over.

“As soon as phosphorous reacts with oxygen it sets alight, which makes it tricky.

“Wiltshire Council did a fantastic job at supplying the skip, which also arrived and a large amount of sand which was used for the controlled explosion.”

Around 15 firefighters from Trowbridge and Warminster and 10 police officers were on site.

Mr Bence said: “They didn’t know how many bottles were underground and it is believed there could be some more, so we have advised the contractors to avoid that area from now on.”

More explosives were found underground by the bomb disposal team from Tidworth than was first expected, which meant the controlled explosion was not carried out until around 12.40am, three hours after the initial expected time.

The decision to carry out the explosion in the town late at night was questioned by explosives expert Dr Sidney Alford, founder of Chippenham-base Alford Technologies.

He said: “I can’t understand why they decided to carry out the explosion the way they did, I guess they must have had good reason.

“I think it would have been more sensible to place the bottles into water so that there was no chance of the phosphorous being released and to take them somewhere such as Salisbury Plain to do it there.”

The site where the explosives were found is being developed for eight homes. Bath developer Shepperton Homes is building eight detached and semi-detached houses on the land.

The derelict house which formerly stood on the site, and which was originally due to be redeveloped as part of the scheme, was severely damaged by a fire last March and eventually demolished.

The homes scheme was due to have been finished last spring but was delayed because of the fire and the subsequent change in the plans for the land.

Thanks to John Kelly, Andy Fox and Trowbridge Fire Station for videos.