The explosion and inferno that destroyed a shop in Leicester is not believed to be related to terrorism, police have said.
Leicestershire Police said officers and Leicestershire Fire and Rescue Service will conduct a joint investigation into the cause of the blast in Hinckley Road.
Huge flames engulfed the Londis store and flat above following the explosion at about 7pm.
Four people have been taken to the Leicester Royal Infirmary, where they are in a critical condition.
In a statement, police said that ‘at this stage there is no indication this is terrorist related’.
Officers added: ‘Businesses and homes in the immediate vicinity have been evacuated and those affected have been taken to Hinckley Road police station as a temporary measure.
‘Four people have been taken to hospital and we await an update on their injuries.’
Power has been cut off for a number of properties in the area, many of which were evacuated by emergency services, officers added.
Dramatic photos and videos posted on social media show witnesses standing on the other side of the road in shock while police officers frantically cordon off the area.
Fire crews said the building, consisting of the shop and a flat above, suffered a ‘pancake collapse’ due to the fireball.
Debris was blasted across the road as the building, which is in a terrace of shops, was completely destroyed.
Firefighters are treating the incident as a search and rescue operation and six fire engines have been requested at the scene.
A Leicestershire Fire and Rescue Service spokeswoman said: ‘This is a search and rescue at the moment. It is unknown if people are injured or trapped.’
She added that the affected property was a two floor building with a loft conversion that had suffered a ‘pancake collapse’.
Houses nearby have been evacuated and the road is closed.
An eyewitness described how onlookers ran down the street and towards the rubble as they feared people were trapped inside.
Jonny Halliwell told the Mirror: ‘People grabbed blankets and ran towards the fire to try to help people. There was rubble and shop fittings everywhere.
‘I saw people pulling up chunks of rubble and searching for people underneath.’
Emergency services received calls from members of the public who reported hearing a blast at about 7.03pm.
Leicestershire Police have advised people to avoid the area while emergency services work at the scene.
University Hospitals of Leicester NHS Trust said four people are in a critical condition and have been taken to the Leicester Royal Infirmary.
Doctors remain at the scene, while a hazardous material response team was also deployed.
It is not clear if anyone was inside the building at the time, or if those injured were outside or in a nearby property.
Many witnesses took to Twitter, with some saying there is a bus stop directly outside the building.
Lauren Girling tweeted: ‘Massive explosion near mine, apparently a shop has exploded and there’s rubble everywhere! Hopefully everyone’s ok!’
Stu Teasdale wrote: ‘The explosion on Hinckley Road doesn’t sound good. Fingers crossed everyone is okay.’
Another local said: ‘Hearing there has been a gas explosion around the Hinckley Road area of #Leicester hope everyone is ok.’
Leicestershire Police said: ‘There has been a major incident on Hinckley Road, Leicester.
‘All emergency services are currently dealing with this. Carlisle Street and part of Hinckley Road have been closed please avoid the area.’