Eight people are not answering phone calls and are believed to be under the rubble of two buildings that collapsed after an explosion early Sunday in the southern French city of Marseille, local officials said.

The cause of the explosion is not yet known, Marseille prosecutor Dominique Lorance said this evening.

The collapse caused a fire, which has complicated rescue efforts and investigations, and was not yet under control, he said during a news conference.

Five people were taken to hospital with serious, but non-life-threatening injuries.

A third building partially collapsed and some 30 buildings in the area were evacuated, said Interior Minister Gerard Darmanen, who visited the scene.

Almost 180 people have been displaced, Housing Minister Olivier Klen told Europe 1 radio.

The buildings that collapsed on Tivoli Street were not known to have structural problems, the prosecutor said.

“Thoughts are with Marseille,” President Emmanuel Macron wrote in a message on Twitter.