Two of the victims were terribly wounded, including a woman believed to be in her 20s who was airlifted to hospital with serious burns.

She had been found on the street by the emergency services after she was blown out of the block of flats.

Witnesses described seeing a huge fireball envelop the building and nearby buildings were shaken by the blast.

‘It was a huge noise and a huge vibration. The building shook, all the window panes shook,’ said 62-year-ancient Pamela Salter, whose home overlooks the flats near the River Severn in Shrewsbury.

‘I reckon we all thought it was a bomb. We looked out of the window and saw a plume of rubble rising in the air.’

Supt Peter Lightwood from West Mercia Police said the scene was one of ‘total devastation’ and added it was lucky no one had been killed.

‘The cause of the explosion is unknown,’ he said.

‘We are aware the casualties woke to the smell of gas.’

Roads near the scene of the explosion were closed and the surrounding area was littered with rubble.

Jim Grindley, who was working nearby, told the BBC: ‘I ran down, the side building was on fire, loads of people were getting dragged out.

‘I just ran straight over to the rubble, just saw a hand come out the rubble, so I just grabbed them and pulled them out. I got told to go away then.

‘It smelled of gas, it was a horrible sight, horrible sight.’