Eight people were missing in the rubble of two collapsed buildings in France’s second largest city, Marseille. Six injured people have been taken out.

Both buildings collapsed after explosions shortly before 1am on Sunday. The cause of the explosion was still unknown as of Sunday afternoon.

Dominique Laurens of the authorities in Marseille said according to AFP that the eight missing people living in the building were not answering their cell phone calls.

The collapse started a fire within the wreckage, complicating rescue work. Extinguishing work must be done carefully so as not to injure people still trapped in the rubble. The intense heat made it impossible to include dogs in the search.

Interior Minister Gérald Darmanin visited the site on Sunday. He estimated that there were still between four and ten people in the ruins.

Mayor Benoit Payan is prepared if there are casualties.

– I want us to be prepared for a difficult situation in which we may experience victims today, said Payan.

So far, six people have been pulled out of the wreckage. Five of them were sent to hospital with serious but non-life-threatening injuries. The sixth received treatment for shock, said Darmanin.

A third building partially collapsed on Sunday. About 80 residents have been evacuated from the surrounding buildings.

The building that collapsed Sunday night is located on Rue de Tivoli. It is not known there should have been any structural problems to the building, according to Darmanin. Laurens did not rule out that there had been a gas explosion.

– My thoughts go to Marseille, wrote President Emmanuel Macron on Twitter. (NTB)