Updated

A Polish prosecutor says that the investigation into a recent house collapse that killed six people centers on the hypothesis of a gas explosion.

Tomasz Orepuk, spokesman for prosecutors in Swidnica, in Poland's southwest, said that the first autopsy carried out Tuesday has shown that the victim, a 39-year-old man, suffocated when crushed under the rubble of the brick house. Five more autopsies were planned for later Tuesday and for Wednesday.

The probe focuses on a gas explosion after witnesses said they first heard a loud bang and then saw the three-floor house collapse, he said.

Prosecutors and experts continue to gather evidence at the site.

Four people were also injured when the pre-World War II house collapsed early Saturday in the southwestern town of Swiebodzice (Shvyeh-'boh-tchi-tseh.)