Superintendent Shane O'Neill, of Leicestershire Police, said: "There are now five confirmed fatalities and a number of people still undergoing treatment in hospital". Specialist search and rescue teams were being supported by two search dogs.
Emergency officials were still on the scene in Leicester, about two hours north of London, on Monday morning, searching a collapsed structure and investigating the cause of the explosion, police said.
"But the fire was getting bigger and bigger so people were told to leave the scene", she said. British police said there was no indication at this stage that the explosion was linked to terrorism. "It is unknown if people are injured or trapped".
"I saw one guy get pulled out and he'll be very lucky if he wasn't killed". The Leicester Mercury said the shop was a Polish grocery called Zabka Leicester and above it was a two-floor flat.
"It's blown the shop across both sides of lanes and there is carnage everywhere".
He added that instead of making divisive comments on social media, people should focus "on what unites us at this moment in time and particularly in the events of this sort of tragedy".
The apparent explosion occurred Sunday evening on a stretch of road containing commercial and residential properties close to the city center.
Matt Cane, Group Manager from Leicestershire Fire and Rescue Service, said emergency staff have worked through the night to locate further survivors or casualties. The sound - I thought it was a bomb!
Mr Kurd said he did not know what happened to the other member of staff.
Hinckley Road was closed between the junction with Woodville Road and Westcotes Drive, while Carlisle Street was also shut. There's just glass everywhere, the road is full of debris, there's plumes of smoke.
The Leicestershire Police Department said in a statement that an investigation into the cause of the blast is ongoing and that they do not believe it is terror-related at this time.