A two-storey building has collapsed in the southern Italian province of Naples, killing two young siblings and their mother, while burying the children’s grandmother under the rubble, firefighters and local media said.

The firefighters said on their official Telegram channel that a gas explosion probably caused the collapse.

Rescuers in the town of Saviano recovered first the bodies of a six-year-old boy and a four-year-old girl, and a few hours later located the body of another victim, identified as their mother, local media said.

Searches are still under way to find the older woman, identified as the grandmother of the children, who was believed to be trapped under the rubble.

Earlier on Sunday, the siblings’ two-year-old brother had been found alive with the father, who was admitted to hospital in Naples in a serious condition.

Firefighters’ spokesman Luca Cari said earlier that rescuers had to be “very careful and move slowly, to avoid new collapses” as they searched for the two women.

Mayor Vincenzo Simonelli was at the scene and told reporters that the building appeared “crumpled up on itself”, adding it was “a very serious situation”.

Media reports said a gas leak could have caused the explosion that rocked the second floor of the building, which crumbled down, covering the lower floor with rubble.