WARSAW, Poland (AP) — Officials in southwestern Poland say two people were killed and four were injured when an apartment house collapsed, and authorities are working to account for 11 others.

Daniel Mucha, spokesman for firefighters in the city of Wroclaw, said the collapse occurred early Saturday in the town of Swiebodzice (Shvyeh-'boh-tchi-tseh). He said the collapse of two floors of the building might have been caused by a gas explosion.

Mucha says more than 20 units of firefighters are searching the rubble.

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