The building next to the four-story apartment building that collapsed in Marseille early on Sunday has partially collapsed as well, French media reported later in the day.

The French 20 Minutes newspaper said the initial collapse took place shortly after midnight in La Plaine District. No severe casualties were reported, and at least two people were injured.

Eleven people have been evacuated so far, according to the Ouest France newspaper, which detailed that nine of those evacuated, including two children, emerged unharmed.

Regional prefect Christophe Mirmand told AFP there were "strong suspicions" that an explosion was behind the collapse, which, in itself, had been possibly caused by a gas leak. "But we must remain very cautious about the causes at this stage."

"It sounded like an explosion," one resident said.

Part of the building, located at 15 Tivoli Street, collapsed later on Sunday morning BFMTV reported, noting that firefighters were still unable to send rescue dogs for the search operations owing to the fire hazard.

Part of the adjoining building located at 15 Tivoli Street collapsed later on Sunday morning, BFMTV said, adding that firefighters were still unable to send in rescue dogs due to fire hazards. 

French President Emmanuel Macron in his tweet expressed sympathy for the people affected by the accident and thanked firefighters and rescuers for their work.

Émotion avec Marseille, où un immeuble de la rue Tivoli s’est effondré cette nuit. Je pense aux personnes touchées et à leurs proches. Les recherches se poursuivent avec d’importants moyens déployés. Merci aux pompiers et aux secours mobilisés.

— Emmanuel Macron (@EmmanuelMacron) April 9, 2023

As a safety measure, authorities evacuated other buildings on the street, with residents using a school as shelter until things are clearer.

Officials revealed that they were probing the incident in a bid to clarify the true reason behind the collapse, with accounts saying there were a hundred firefighters on the site. "The priority is to extinguish the fire and clear the rubble to find people possibly underneath it," the commander of the marine firefighters said.