Around 50 people were evacuated from their homes early today after a suspected gas explosion, police said.
No one was injured in the blast which ripped through a block of flats in Runcorn, Cheshire, at around 5.25am.
Cheshire Police said residents living close to the scene in Richard Close, Castlefields, reported the smell of gas at the time of the explosion and an investigation is under way into the cause.
Most of the occupants have been moved to a nearby community centre and all roads remain open, the force added.
Police said later they believe the explosion was caused when copper piping was stolen from the building.
Sergeant Simon Hignett said: "It is a miracle no one was injured as a result of this explosion.
"The cause is believed to be down to copper piping being stolen and I am keen to speak to anyone who may have seen people acting suspicious in the area.
"How people can be so reckless and put lives at risk in order to steal some metal is beyond me and these people need to be caught."
Anyone with any information about the theft which is believed to have led to the explosion is asked to call Cheshire Police on 0845 458 0000 or Crimestoppers anonymously on 0800 555 111.