Leicestershire Fire and Rescue said six fire engines were responding and the incident is being treated as a search and rescue operation.
British police declared a major incident on Sunday after a large blast destroyed a convenience store and a home in the central English city of Leicester.
Pictures and videos posted on Twitter showed flames leaping into the sky above the city and the remains of what some witnesses said was a convenience store and a house that had been destroyed in the blast.
"All emergency services are currently dealing with this," the police force said in a statement. "Please avoid the area."
The city's fire department sent six fire engines after reports of a large explosion and a building collapse.
"We got a call about an hour ago after reports of a large explosion and a building collapse," a firefighter in the city's fire department's control room said.
A picture used by the Leicester Mercury newspaper showed a blaze above the rubble of the destroyed building, which housed a convenience store and a flat above it.
"We heard an absolutely massive explosion. It was pretty frightening," the newspaper quoted an unidentified resident who lives a few streets away.
"We went to look out of the upstairs windows and saw loads of smoke, and then a few seconds later massive orange flames."