At least 8 people are missing on Sunday after the collapse of a building in the center of Marseille from an explosion the cause of which is unknown and which also injured five, French authorities said.

“We have eight people that we have not been able to reach (…). We have no news about them,” Dominique Laurens, the public prosecutor of the Republic in Marseille, southeastern France, told a press conference in the afternoon.

The building collapse in the center of France’s second most populous city occurred in the early hours of Sunday.

“Tonight at 00:40 (22:40 GMT on Saturday) there was a collapse of a building at 17 Tivoli Street, causing part of (the buildings at) 15 and 19 Tivoli Street to fall,” he told the press Benoît Payan, mayor of this port city.

“We must be prepared for casualties in this terrible tragedy,” Payan said after the four-story building collapsed.

He added that they have counted five injured so far, although none of them are in serious condition.

According to the prosecutor’s office, which reported a possible ninth missing person, they managed to identify the missing, which did not include children or minors, because their relatives were unable to contact them.

Marseille’s prosecutor acknowledged that “it is currently impossible to know the causes of the explosion” which destroyed the building and which occurred at 00:46 (22:46 GMT on Saturday), according to surveillance cameras.

“Gas is clearly one of the clues” authorities are considering, he added.

“It was huge, like an explosion,” Gilles, a man who preferred not to give his last name and who lives on a street perpendicular to the collapsed building, told AFP.

Since early Sunday morning, the fire brigade has been trying to extinguish the fire, so that rescuers and sniffer dogs cannot search for the missing among the rubble.

A photographer from the AFP observed a large cloud of smoke on Sunday afternoon.

French President Emmanuel Macron expressed his “excitement” at this tragic event.

Eight people were killed in the collapse of two buildings on Rue Aubagne, also in the center of Marseille, in November 2018. These buildings were in a serious state of unsanitary conditions.