Eight people are not responding to calls and are thought to be under the rubble of two buildings that collapsed in an explosion early on Sunday in the southern French city of Marseille, local officials said.
The cause of the explosion was not yet known, Marseille prosecutor Dominique Laurens said on Sunday evening.
The collapse caused a fire that complicated rescue efforts and investigations, and that had not yet been brought under control, she told a news conference.
Five people were taken to the hospital with serious but not life-threatening injuries.
A third building partially collapsed and some 30 buildings in the area were evacuated, said Interior Minister Gerald Darmanin, who visited the site of the disaster.
The search for victims continues
Some 180 people have been evacuated, Housing Minister Olivier Klein told Europe 1 radio.
The buildings that collapsed on the Rue de Tivoli were not known to have any structural problems, the prosecutor said.
"Thoughts are with Marseille," President Emmanuel Macron said in a Twitter message.