Four people have died after a tragedy at a Norfolk building site saw them crushed beneath tonnes of falling steel.

The men were working four metres below ground when the steel structure they were building collapsed on top of them.

Police and safety inspectors have launched an investigation into the tragedy, which happened in the Runham area of Great Yarmouth.

Emergency services were called to the industrial site at North River Road at about 2.20pm yesterday afternoon.

Firefighters and three air ambulances went to the site, owned by engineering company Claxton, in North River Road.

But there was nothing they could do to help the men, who were buried beneath tonnes of collapsed metal and were pronounced dead at the scene.

All four are believed to be from the Bury St Edmunds area and aged between 26 and 42.

A local crane firm was called in to lift the metal so the bodies of the workers, who worked for an external contractor, could be reached.

A spokesman for Claxton, which provides drills for off-shore oil rigs, said: 'Claxton Engineering Services Limited can confirm that an accident occurred at its premises in North River Road, Great Yarmouth where construction work on a new facility is being carried out by external contractors.

'We are also able to confirm that four men have tragically lost their lives in this incident which is now being investigated by the Norfolk Constabulary and the Health and Safety Executive.

'The company is fully cooperating with the investigation.

'Everybody at Claxton is deeply saddened by what has occurred and the company's thoughts and sympathy are with the families of the four men.'

A spokesman for The East of England Ambulance Service confirmed: 'We were called to a serious incident in Great Yarmouth this afternoon where a steel structure which was being built four metres below ground to reinforce building foundations collapsed while four workers were inside.

'Land and air ambulance crews have worked closely with the other emergency services.'

Nine fire crews were called to the scene, including a heavy rescue tender from Norwich, crews from Great Yarmouth and search and rescue teams.

An investigation has been launched by the joint Norfolk and Suffolk Major Investigation Team (MIT) working with the Health and Safety Executive (HSE).

MIT Det Chief Inspector Neil Luckett said: 'This is a tragic event and we will be working closely with the HSE to establish the full circumstances surrounding the incident.

'This may be a lengthy process. Our thoughts our with the families of the men who died yesterday.'

Police were last night informing family members of the tragedy.

Two football clubs have cancelled their matches today out of respect to the men who had links to Walsham Le Willows Football Club in Suffolk.

Mike Powles, chairman of the Walsham Le Willows FC, said: 'The Walsham and Stanton games have all been called off due to the fact the men killed in the tragic accident were from the local area and had been involved in both the clubs.'Joy Mayhew, secretary at Stanton FC, said two of those who died were due to play against Grundisburgh today.

She said: 'It is a complete feeling of disbelief.'A spokesman for the Health and Safety Executive confirmed inspectors had gone to the scene and it is expected that HSE officers will spend today trying to piece together what happened.

Police set up a seal keeping the public back at least 100 yards from the scene of the accident. One vehicle remained at the scene overnight.

Claxton, which provides drills for off-shore oil rigs, was set up in 1985 by Bob Claxton and celebrated its 25 anniversary last year.

It has a 100-strong workforce at its main base remains in Great Yarmouth, but bases have also been established in Aberdeen and, most recently, in Dubai.

Claxton became part of Norwich-based service group Acteon in 1999, but Laura Claxton remains managing director and Dannie Claxton is the technical director.

The construction work was to put in place foundations for a new building, because the successful company was expanding.

The company has won industry awards, including the Queen's Award for Export Achievement, in 1998, to the Spirit of Enterprise 'Great Engineering Company' Award in 2009.