Police updated the death toll after finding another body among the rubble before they were forced to pause rescue efforts amid fears a neighbouring property could collapse.
Police declared a "major incident" after the explosion occurred last evening on a stretch of road containing commercial and residential properties in Hinckley Road area of Leicester, some 140 km away from London. The city has a large Gujarati-origin population.
"Although the cause of the explosion is not yet known, there is no evidence that this is linked to terrorism," said Superintendent Shane ONeill of Leicestershire Police.
"There are now five confirmed fatalities 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," he added.
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Matt Cane, group manager at Leicestershire Fire and Rescue Service, said the bodies of the four people were found during the search of the building.
British police said there was no indication at this stage that the explosion was linked to terrorism.
"The cause of the explosion will be the subject of a joint investigation by the police and Leicestershire Fire and Rescue Service," police said in a statement.
"We would ask that the media and public do not speculate about the circumstances surrounding the incident, but at this stage there is no indication this is terrorist related," it said.
A fire service spokeswoman said the property was a two-floor building with a loft conversion that had suffered a "pancake collapse".
The emergency services have cordoned off about 60 houses in the area, which was a mix of apartments and small shops, including a convenience store, a kebab restaurant and a Polish grocery.
Eyewitnesses said there was thick smoke in the area. One neighbour said she heard "this big thud, like an earthquake."
She said she and others helped a boy, believed to be aged about 15, who was hurt in the blast.
"He was in there when it happened. I think he was in the flat above the shop. We were keeping him warm and assuring him he'd be OK and the ambulance would be there," she said.
Harish Pattni, who was in a pizza shop which was six shops down when the explosion occurred, described the vibrations from the blast.
"The flames started more or less upstairs so I thought it must be something to do with upstairs, the flats. My immediate worry was when I saw the floorboards, all the wood on the floor level, I thought there must be people in the shop trapped," he said.
The building affected is in a row of shops and debris from it was blasted across both carriageways of the road.