Local firefighters' spokeswoman Patrycja Pokrzywa said the blast destroyed the detached house — home to two families — shortly after 6 p.m. (1700 UTC) on Wednesday evening.
Children were believed to be among those trapped in rubble. Fires in the debris had been dealt with by dozens of firefighters assisted by rescuers with dogs, she said.
A leak in a local gas pipeline was probably responsible, said Artur Michniewicz, a Polish gas company spokesman.
For safety reasons, authorities had cut off gas to a large part of the town, he added.
Mound of bricks
Footage on Polish TVN24 broadcasting showed rescuers trying to access a mound of bricks left by the collapse amid freezing temperatures and snow.
The mayor of Szczyrk Antoni Byrdy said the search was likely to continue into Thursday morning.
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ipj/se (AP, Reuters)