An explosion in Paris has levelled a four-storey apartment building, killing six people including three children and leaving others trapped in rubble.

Rescue teams working with sniffer dogs searched through what remained of the building in Rosny-sous-Bois, trying to find two people missing.

Among the victims were a 10-year-old boy, a mother and two children aged between 14 and 18. The bodies of a 45-year-old woman and another adult were also recovered.

Sorry, this video has expired Six people were killed when an explosion levelled the Paris apartment building.

Eleven people, four of them seriously wounded, were rescued, he said.

Gaetan de Raucourt, head of the Paris firefighting department, said there was still hope that occupants had found "pockets of air" amid the wood and concrete which was piled a storey high and fanned out into the street.

"People might be sheltering there. We still have hope of finding survivors," he said.

Emergency crew chief Bernard Tourneur said the search would continue for at least 24 hours with care, since the remainder of the building left standing "is threatening to cave in".

One side of the building was ripped off, exposing the interiors of the apartments. Early indications were that it was caused by an accidental gas explosion.

"Our house moved. We were trembling from fear," said Pauline, a neighbour who lives 100 metres from the collapsed building.

She said the explosion was so loud that "our ears were ringing".

Locals run into street to help victims

French firefighters search the rubble of the collapsed building in Rosny-Sous-Bois ( Reuters: Christian Hartmann )

Ghislaine Poletto, 55, who lives about 50 metres away, said she "jumped into her trousers" and hurried to the site where together with neighbours "we managed to pull two children out".

One of the children was "protected by a mattress and a board above his head which saved his life", she said.

Another resident, Arafet Brahim, said he and his friends pulled out some children who appeared to be in good shape.

"We tried to take people out," he said. "But we also took bodies out. Frankly it was horrible. I don't know how to describe that moment."

Interior minister Bernard Cazeneuve said the explosion around 7:00am (local time) appeared to have been caused by a gas leak.

"We should be prudent, because there are investigations ongoing. There is no certainty," he said.

Mr Plus said gas and electricity works were on site but would not confirm their link to the disaster.

GRDF, the company in charge of delivering gas to homes, told AFP that "no leaks had been reported previously" in the area.

Neighbour Maryline Yyvon suggested otherwise.

"They'd been digging under the sidewalk just in front of the building," she said.

"Given the force of explosion, it wasn't just a gas canister that's for sure."

Local authorities said the structure itself appeared to conform to building codes.

Reuters/AFP