Six people were injured, two of them critically, after a suspected explosion and subsequent fire destroyed a shop.
Police declared a major incident after the blast in a street in Leicester on Sunday night.
Video taken at the scene shows flames billowing into the night sky as the fire engulfed what is believed to be a convenience store.
One clip appeared to show emergency services rushing to help someone close to flames that were visible from a distance.
Six casualties were been taken to Leicester Royal Infirmary, the hospital said.
A spokesman added: “Two of these patients are in a critical condition, while four are walking wounded.”
A hazardous area response team and ambulance crews remain at the scene in Hinckley Road in the west of the city, it added.
Speaking to Sky News, Kat Pattinson who lives on the same road as the fire, said: “We are down the same street – about 500 metres from where the blast has taken place and our whole house shook.
“We checked on our children first and foremost and then we went outside.
“There is just an awful lot of smoke here at the moment and the whole area is cordoned off.”
She added that the shop on fire is usually open until about 9pm on a Sunday, and has a flat above it.
Leicestershire Fire and Rescue said at around 7.03pm it received calls from the public who said they had heard a blast on Hinckley Road.
A spokeswoman said six fire engines had been requested and that the incident was being treated as a search and rescue operation.
She added that the affected property was a two floor building with a loft conversion that had suffered a “pancake collapse”.
Leicestershire Police tweeted: “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.”
Witness Tahir Khan said: “I was driving past when it happened.
“Loads of people were gathered and there was gas and flames coming out of the building.
“I looked on the road and half the building was on the road. Literally the whole of the side of the building had been blown out.
“I couldn’t believe it, it was like a Hollywood movie.”
BBC journalist John Alexander said: “I live about 80 yards away from where it happened.
“I felt a tremor, what felt like an earthquake shock and I heard a very low boom that sounded like a very, very fast release of pressure.
“I thought my house was going to fall down on top of me and all my neighbours have said the same thing.
“I saw one guy get pulled out and he’ll be very lucky if he wasn’t killed.”