French rescue workers were searching into the night Monday for possible victims under the wreckage of two dilapidated buildings that suddenly collapsed in the centre of Marseille.
Officials in the southern port city warned there were likely casualties after the two adjoining buildings collapsed around 9.00 am (0800 GMT), blocking the street with massive piles of rubble in a scene resembling the aftermath of an earthquake.
"What's important is that there are as few deaths as possible, but we think there will be some," said Marseille Mayor Jean-Claude Gaudin.
Housing Minister Julien Denormandie, who rushed to Marseille from Paris, said it was a "race against the clock" to find survivors.
Some 100 rescue workers with sniffer dogs were combing the rubble "relentlessly", Denormandie said, while a drone scanned the wreckage from above.
Just two passers-by were reported lightly injured in the morning.
The delicacy of the operation, a stone's throw from Marseille's bustling Old Port and waterfront, became clear in the afternoon when part of a third adjoining building collapsed.
Authorities had evacuated several dozen residents from neighbouring buildings as a precaution, police spokesman Philippe Bianchi told AFP.
Google Maps images taken in recent months showed the two collapsed buildings, in the working-class neighbourhood of Noailles, had had large visible cracks in their facades.
One of them had been condemned and, with its windows boarded up, was well-secured and in theory unoccupied, officials said.
But neighbours feared there were people inside the other when it crashed down in what Djaffar Nour, who was grocery shopping down the street, said was "a matter of seconds".
"There was a Comorian lady -- every morning she took her two children to school and she got back just before the explosion," said Nacer Sellani, manager of a shop across the street.
He added he had seen two other people arriving to visit one of the tenants in the building, which had 12 apartments, nine of them occupied, according to rescuers.
CCTV footage showed two people walking past the buildings at the moment when they came crashing down.
'Homes of the poor'
French President Emmanuel Macron said Marseille had "the solidarity of the nation" as rescuers worked into the darkness.
The incident -- rare in a major Western city -- has already sparked a political row over the quality of housing available to Marseille's poorest residents.
The neighbourhood is home to many buildings in a similarly poor condition, some of them run by slum landlords.
"It's the homes of the poor that are falling down, and that's not a coincidence," said local lawmaker Jean-Luc Melenchon, leader of the left-wing France Unbowed party.
Marseille authorities launched a vast upgrade plan for the city centre in 2011.
But a 2015 government report said some 100,000 Marseille residents were living in housing that was dangerous for their health or security.