Six people have been taken to hospital after reports of an explosion and a fire in the Hinckley Road area of Leicester.
Police declared a “major incident” after reports of a blast just after 19:00 GMT.
A police spokesman said: “At this stage there is no indication this is terrorist related.”
Carlisle Street and part of Hinckley Road have been closed and people are being asked to avoid the area.
Two of the six people taken to hospital are in a critical condition and the other four are “walking wounded”, according to the University Hospitals of Leicester NHS Trust.
Angel Namaala lives opposite the scene and told the BBC she had heard “this big thud, like an earthquake”.
She added: “The building had gone down and people were trying to help where they could by taking the bricks off. But the fire was getting bigger and bigger so people were told to leave the scene.”
Six fire engines have been at the scene, Leicestershire Police said. Flames could be seen rising from a building in the middle of a parade of shops.
BBC journalist John Alexander said the explosion had “blown debris and rubble across four lanes of traffic”.
He said the emergency services had cordoned off about 60 houses in the area and people had been evacuated because of an “enormous” fire.
A Leicestershire Fire and Rescue Service spokeswoman said they were involved in a “search and rescue” operation.
The affected property was a two-floor building with a loft conversion that had suffered a “pancake collapse”, she said.
All of the casualties have been taken to Leicester Royal Infirmary, the ambulance service said, and crews remain at the scene.
People have been asked not to attend A&E services locally unless “absolutely necessary”.
Alpana Marwaha, who lives near the scene, told the BBC: “I heard a bang and the house shook. We could see the flames.
“You can still see the smoke coming, and the emergency services. There are a few shops there and it is surrounded by houses,” she added.
East Midlands Ambulance Service said that crews from the West Midlands and Yorkshire had responded to other 999 calls near the border while they dealt with the incident in Leicester.
You can also contact us in the following ways: