An explosion in an ambulance rocked St Helier Hospital, forcing 200 patients, staff and visitors to be evacuated.

One firefighter was injured when gas cylinders aboard the emergency vehicle ruptured and exploded blowing out nearby windows, shaking the building and shuddering the homes of residents more than a mile away in Sutton.

Flames and thick black smoke was seen billowing from the vehicle parked near in a main thoroughfare near the pathology laboratory and maternity ward at about 4.50pm on Tuesday.

Patients, doctors, nurses and visitors from nearby wards were told to evacuate with many left to huddle outside in blankets as fire fighters cordoned off a large zone around the hospital fearing other medical gas supplies could ignite.

Fireman Omar Qureshi, 27, from Sutton, was within a metre of the ambulance when its cylinders blew and suffered minor burns.

He said: “I’m fine, my protective outfit stopped me from getting any serious injury. We had the fire out quickly.”

Health chiefs said three members of staff suffered minor injuries, but no patients were injured. The explosion left the ambulance as a shell and another ambulance parked opposite was also damaged.

Hospital visitors told how the drama unfolded.

Colin Johnson, 42, an electrician from Cheam, whose son Oscar, five, was having surgery at a nearby hospital building said: “I was waiting for the lift when I heard the noise and the whole building shook.

“I thought a skip had been dropped from a crane or something. I went to the window and saw the ambulance on fire.”

Road sweeper Michael Cornwell, 21, was working opposite the hospital when the force of the explosion hit him.

He said: “I first saw the smoke billowing out of the hospital; big thick smoke.

“Then five minutes later there was an explosion, it was like a bomb going off.

“It went right through me and shook me where I was standing.”

Patients rallied round to help each other get clear of the hospital during the evacuation.

Amanda Duggan, 45, a housewife from Banstead, was waiting with her son Sam Duggan, 22, in A and E when patients were told to evacuate.

Together the pair rescued fellow patient James Miller, 31, who was left alone and stranded and found him a wheelchair to help him escape.

She said: “We didn’t really know what was happening, it was almost like those who could walk could go and those who couldn’t were left.

“Later there were people telling us what to do, but at the beginning it wasn’t clear so we found him a wheelchair and took him outside, it was quite unnerving.”

London Fire Brigade spokesman Sam Kazmanli said as the fire brigade arrived two cylinders in the ambulance ruptured.

He said investigations were underway as to why the fire began.

He said: “Our thermal imaging shows six cylinders in the ambulance and two ruptured.”

Fireman had the scene under control by 6.40pm and the road was open to traffic again at about 7pm.

Peter Coles, chief executive of Epsom and St Helier Trust said: “We are unable to confirm at this time what caused the fire. However, we will be working with the relevant organisations to help understand what happened.”

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