Rescuers search after a building collapsed burying several people in Swiebodzice, on April 8, 2017. At least three people were killed and four injured on Saturday when an apartment house collapsed in western Poland, possibly due to a gas explosion, according to officials. / AFP PHOTO / NATALIA DOBRYSZYCKANATALIA DOBRYSZYCKA/AFP/Getty Images

Rescuers search after a building collapsed burying several people in Swiebodzice, on April 8, 2017. At least three people were killed and four injured on Saturday when an apartment house collapsed in western Poland, possibly due to a gas explosion, according to officials. / AFP PHOTO / NATALIA DOBRYSZYCKANATALIA DOBRYSZYCKA/AFP/Getty Images

Rescuers search after a building collapsed burying several people in Swiebodzice, on April 8, 2017. At least three people were killed and four injured on Saturday when an apartment house collapsed in western Poland, possibly due to a gas explosion, according to officials. / AFP PHOTO / NATALIA DOBRYSZYCKANATALIA DOBRYSZYCKA/AFP/Getty Images

Rescuers search after a building collapsed burying several people in Swiebodzice, on April 8, 2017. At least three people were killed and four injured on Saturday when an apartment house collapsed in western Poland, possibly due to a gas explosion, according to officials. / AFP PHOTO / NATALIA DOBRYSZYCKANATALIA DOBRYSZYCKA/AFP/Getty Images

Rescuers search after a building collapsed burying several people in Swiebodzice, on April 8, 2017. At least three people were killed and four injured on Saturday when an apartment house collapsed in western Poland, possibly due to a gas explosion, according to officials. / AFP PHOTO / NATALIA DOBRYSZYCKANATALIA DOBRYSZYCKA/AFP/Getty Images

Two people have died and four others were injured after an apartment house collapsed in south-western Poland, with 11 other people missing.

The collapse occurred early on Saturday in the town of Swiebodzice, according to Daniel Mucha, a spokesman for firefighters in the city of Wroclaw.

He said the collapse of two floors of the building might have been caused by a gas explosion.

Mr Mucha added that more than 20 units of firefighters are searching the rubble.

TVN24 live footage showed rescuers in helmets searching through bricks and splintered wood.