"At the moment, we are clearing the buildings next door, taking care not to endanger the people who could be beneath the rubble," the mayor said.
In the surrounding buildings, more than 30 residents were "affected", while five were injured. All evacuees were currently sheltering in schools and nurseries.
Regional prefect Christophe Mirmand told AFP there were "strong suspicions" that an explosion caused the collapse, possibly a gas leak.
A late-night food vendor working on the street said "everything shook" during what sounded like an explosion.
"We saw people running and there was smoke everywhere," said Aziz, who declined to give his last name.
Gilles, who lives on a side street near the fallen building, told AFP the sound of the crash "was huge".
"It sounded like an explosion," said Gilles, also declining to provide his last name.