A police spokesman said a blast in the Czech capital Prague was probably caused by gas and that there had been about 15 people in the building.
There have not been reports of any deaths, a fire department spokeswoman said.
The explosion, close to Prague's National Theatre, was heard as far as Prague Castle about a mile away.
Windows in neighbouring buildings were blown out, including Prague's landmark Cafe Slavia.
The head of the rescue service attending an explosion in central Prague has said that up to 40 people have been injured.
Police have said that people are also believed to be buried under rubble, the Associated Press reports.
Anna Zamejc, a freelance journalist, who lives near the scene of an explosion in the old city of the Czech capital Prague, reports that witnesses have said that flats at the explosion site were "totally destroyed".
At least 13 people have been injured after a powerful explosion damaged a building in the centre of the Czech capital Prague.
A powerful explosion has damaged a building in the centre of the Czech capital Prague, the Associated Press reports.
Police spokesman Tomas Hulan said it is not immediately clear what caused the blast and it is believed some people are buried in the rubble.
At least 13 people have been injured, fire service spokeswoman Pavlina Adamcova said.
Windows in buildings located hundreds of metres from the blast were shattered, including some in the nearby National Theatre.
Presiding judge Tomas Kubec ruled that Randy Blythe's actions did not constitute the crime of causing an injury leading to death.
"We did not find criminal responsibility in the actions of the defendant," he said. "We found moral responsibility. There has been the death of a young man who had not been guilty of anything."
Kubec said the concert promoters were ultimately to blame for failing to prevent fans from clambering onto the stage.
"We reached the conclusion that there was a serious fault on the side of the promoter and organiser of the concert."
Prosecutors immediately appealed against the acquittal, meaning that the case will be reviewed by the Czech High Court.
Randy Blythe, singer of US metal band Lamb of God, was today acquitted of charges of causing the death of a fan.
He posted the above photograph shortly after the verdict of the court in Prague, along with the following message:
"I have been found not guilty & acquitted of all charges against me. I am a free man. This photo was taken by my friend@aceyslade- it says it all.
"Please remember the family of Daniel Nosek in your thoughts & prayers in this difficult time. I only wish for them peace. Thank you for your support- Randy."
A Czech court has acquitted the frontman of US heavy metal band Lamb of God, Randy Blythe, of charges he caused the death of a fan at a concert in Prague three years ago.
The prosecution had accused Blythe, 42, of causing the death of the 19-year old fan by pushing him off the stage at a 2010 concert.
Leftist former prime minister Milos Zeman won the Czech Republic's first direct presidential election, partial results showed today.
Mr Zeman, 68, was leading by 55.8 to 44.2 per cent over Foreign Minister Karel Schwarzenberg, a prince from a centuries-old aristocratic family, results from 93.75 percent of voting districts showed.
Czech President Vaclav Klaus has been shot with a replica pistol during a walkout in the north of the country. He suffered minor bruising in the attack.