A number of people were injured after an explosion in a town centre yesterday, police said.

A building collapsed in Shrewsbury, UK, in what was believed to be a gas explosion, a spokesman for West Mercia Police said.

Police, ambulance and fire services all attended the scene, which was cordoned off after the late-morning incident.

The spokesman said: "We have a number of casualties and it's been declared to be a major incident. The scene is quite bad."

The explosion happened at a block of flats on the corner of Bridge Street and Smithfield Road, near Welsh Bridge, police said.

Until yesterday evening there were known to be three casualties, two of whom have serious injuries.

One was taken to Selly Oak Hospital in Birmingham suffering severe burns while the other was taken to the Royal Shrewsbury Hospital with spinal injuries. Roads near the scene of the explosion were closed and drivers were warned to expect long delays and congestion.

Pamela Salter, 62, whose flat overlooks the area, described how her building shook with the force of the explosion.

She said: "I think everyone heard it. It was a huge noise and a huge vibration. The building shook, all the window panes shook. I think we all thought it was a bomb. We looked out of the window and saw a plume of rubble rising in the air. It was incredible. And that was before the smoke and fire."

The end of the building where the explosion took place was blasted away altogether and the rubble was strewn right across the road, she added. A total of nine people suffered minor injuries, police said later. These casualties were either dealt with by paramedics or at the Royal Shrewsbury Hospital, a spokesman said.

Two people were seriously injured in the explosion, emergency services said.

Speaking at the scene, a West Midlands Ambulance Service spokesman said a woman in her early 20s was blown out of the building from the first floor and suffered serious burns. Emergency services found her lying in the street outside.

A man, who was believed to have been on the ground floor and had become trapped by rubble, was taken to the Royal Shrewsbury Hospital with suspected spinal injuries, the spokesman said.

Five other people, who were in a car outside the building when the explosion happened, were trapped by rubble and pulled free by bystanders, he said.