This picture of the blast aftermath was supplied by the West Midlands Ambulance Service

Investigators were today still trying to establish the cause of a massive explosion which left 12 people in hospital – three seriously injured.

A gas leak is believed to have been the cause for the blast, but there was not believed to be any gas connected to a shop which was being renovated on the ground floor or flats above it.

The exact cause of the explosion is now being investigated by the Health and Safety Executive and police.

The explosion happened at the junction of Smithfield Road and Bridge Street yesterday morning.

A HSE spokeswoman said: “The Health and Safety Executive was made aware of the incident yesterday and is investigating. The HSE has visited the site this morning to begin preliminary inquiries.”

Speaking at a press conference at Monkmoor Police Station today, Superintendent Martin Whitelegg, from West Mercia Police, said: “We are working with the Health and Safety Executive and they have taken charge of the investigation into the explosion in Bridge Street.

“They tell me a probable cause is a gas leak and they are investigating that as we speak. We will be looking to work with them on an investigation and open up areas of Shrewsbury as soon as possible.

“We don’t believe gas canisters to be the cause at this particular time although the cause is still being investigated. We believe it’s due to an escape of gas.

“We’ve spoken to both the owner of the premises and lease holders of premises in connection with the investigation and are looking at what was going on at the premises.”