Four people have died after an explosion and subsequent fire at a shop in Leicester, police have confirmed.
Four others remain in hospital, one with serious injuries.
The sudden blast took place at 7pm on Sunday about a mile west of the city centre and saw police cordon off around 60 homes on Carlisle Street and Hinckley Road.
Leicestershire Fire and Rescue sent six fire engines to the scene, and said the building had suffered a "pancake collapse".
Firefighters worked through the night to dig through rubble and tackle the explosion's subsequent blaze.
Police believe there may still be people unaccounted for after the incident, and emergency crews are continuing a "search and rescue" operation at the site on Hinckley Road.
Residents reported hearing a low booming sound and feeling their houses shake when the explosion first occurred.
The three-storey shop at the centre of events on Hinckley Road, with a residential flat situated above it, suffered a "pancake collapse" as a result of the incident, according to a fire and rescue spokesman.
Superintendent Shane O'Neill, of Leicestershire Police, said: "There are four confirmed fatalities at this stage and a number of people still undergoing treatment in hospital.
"The building consisted of a shop premises on the ground level and a two-storey flat above it. We believe there may be people who have not yet been accounted for and rescue efforts continue in order to locate any further casualties.
"Once the site is deemed to be safe a joint investigation with Leicestershire Fire and Rescue Service will begin looking into the circumstances surrounding the incident, which at this stage is not being linked to terrorism."
Andrew Brodie, the assistant chief fire officer for Leicestershire Fire and Rescue Service, described the "tremendous effort" of crews as they continued to dig through rubble and tackle the blaze.
Mr Brodie also said on Twitter that work was continuing to ensure those directly affected by the incident were being looked after.
He had earlier described conditions for firefighters as "arduous" on a "bitterly cold night".
Matt Crane, group manager at Leicestershire Fire and Rescue Service, said firefighters would be on the site for "a number of days" and it was "still too early to say" what caused the explosion.
There was the potential for further collapse, and buildings on either side have sustained damage, he said.
He said: "On arrival there was a significant fire and significant building collapse, reports of numerous people possibly trapped within the building so crews have worked throughout the night to extinguish the fire.
"We now have got specialist search and rescue teams supported by search dogs on scene. We are trying to locate any further casualties that may be in the building. We still think this is a rescue phase of the operation.
"We are now working to get into different areas of the building using shoring techniques to see if we can locate anybody that may be alive in the building."
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."
Witness Tahir Khan told the Press Association: "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."
One 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."
Police said an investigation will take place to establish the cause of the explosion.
