Two bodies were found in the rubble of a building that collapsed in Marseille following a major explosion, the fire department announced on Monday morning.
"Given the particular difficulties of intervention, the extraction (of the bodies from the site) will take time," the department said in a brief statement, confirming reports in local media.
Five people from neighbouring buildings were hurt in a possible explosion that destroyed the four-storey block at around 12:40 am (2240 GMT Saturday).
The cause of the explosion is still to be determined, but investigators are looking at the possibility that a gas leak caused it, after reports from local people of a gas smell.
Emergency workers continued rescue operations at night with the help of a crane and lights, but a persistent fire underneath the rubble has hampered their work.
Firefighters said the conditions made it difficult to deploy sniffer dogs, which had not yet found any victims.
Local prosecutor Dominique Laurens told reporters that eight people "were not responding to phone calls", saying it was impossible so far to identify the cause of the collapse.
A gas explosion was "clearly" one of the possible causes, she added.
Multiple witnesses described the blast to AFP .
"I was sleeping and there was this huge blast that really shook the room. I was shocked awake as if I had been dreaming," said Saveria Mosnier, who lives in a street near the site in the La Plaine neighbourhood.
"We very quickly smelled a strong gas odour that hung around, we could still smell it this morning," she added.
Deputy mayor Yannick Ohanessian told journalists at the scene that "several witnesses have reached us this morning to say there was a suspicious smell of gas".
Marseille mayor Benoit Payan thanked rescue workers on Twitter and said they were "determined" to find survivors. "We must hold on to hope," he said.
More than 100 firefighters were battling the blaze in the ruins of the building, believed to have one apartment on each floor.
Interior Minister Gerald Darmanin, who visited the scene, said it would be "several hours... maybe even longer" before the fire was out.
Two buildings next to the destroyed property were severely damaged, with one collapsing later in the day without injuring any rescuers.
Almost 200 residents have been evacuated and 50 have requested to be urgently rehoused.
An aid centre for people looking for missing family members or loved ones has been opened in a neighbouring district.
Cause of blast unclear
"A lot of families in the neighbourhood are afraid," said Arnaud Dupleix, the president of a parents' association at the nearby Tivoli elementary school, which sprang into action to coordinate aid for those evacuated.
In 2018, eight people were killed in Marseille when two dilapidated buildings in the working-class district of Noailles caved in.
That disaster cast a harsh light on the city's housing standards, with aid groups saying 40,000 people were living in shoddy structures. But authorities appeared to rule out structural issues in the latest collapse.
"There was no danger notice for this building, and it is not in a neighbourhood identified as having substandard housing," said Christophe Mirmand, prefect of the Bouches-du-Rhone region.
