A man has been killed following an explosion at an construction site in Hertfordshire yesterday.

Emergency services were called to the Mundells, an area near Welwyn Garden City, shortly after 3pm.

An argon cylinder exploded inside a building still under construction. Crown House Data Solutions, a Laing O'Rourke company, is the main contractor on the site.

Seven other men were injured by the blast and received treatment at Queen Elizabeth II Hospital in Herts. Two are in a serious but stable condition and all others have been treated and discharged.

Laing O'Rourke said it was providing support and counselling to the family of the deceased. His name has not yet been released.

Crown House managing director Liam Cummins said: "This is a tragic event and our thoughts are with the family of our colleague who has tragically lost his life and with those who have been injured.

"I would also like to pay tribute to the emergency services who displayed exemplary professionalism in dealing with this incident."

The cause of the explosion is not confirmed, but it is believed a cylinder of gas depressurised, which acted like a missile and set off the other cylinders.

Each cylinder weighs about 50kg and is about 5ft tall. Reports have claimed as much as 50 per cent of the building's internal structure was destroyed in the incident.

Police and the Health and Safety Executive are investigating.