PRAGUE, March 22 (Xinhua) -- A fire hit a three-story residential building in the Czech city of Usti nad Labem, 80 km north of Prague on Thursday.

Czech regional healthcare spokesman Ivo Chrastecky said that 11 children and nine adults are in hospitals for serious smoke inhalation.

The fire started after 6 a.m. local time, mainly on the second floor of an apartment house located at Hrbovicka street in Predlice district.

It took the firefighters around 40 minutes to get the flame under control and almost two hours to completely put out. "The corridor was full of smoke, until the last minute we could not figure out how many people were inside," said the Fire Chief Michal Nejedly.

As many as 20 people were injured, among them four children and two adults were resuscitated on the scene by the crew members. The investigators said children in the building were mainly affected as the fumes spread and reached them at the above area where they slept.

The cause of the fire is still being investigated.