Rescue workers Monday recovered a fourth body from the rubble of a collapsed apartment in France's Marseille, a cabinet minister said, as firefighters raced against the clock to find four people still missing.

More than 24 hours after a suspected explosion at the building, where residents reported a strong smell of gas, dozens of civil defense staff and sniffer dogs worked among the debris as a fire still smoldered.

"Four bodies have been found," Housing Minister Olivier Klein said, at the site of the accident.

But the deputy mayor of the Mediterranean port city, Yannick Ohanessian, said rescue workers still had hope of finding survivors.

"Until the very end, we will believe it is possible -- even if chances become slimmer with every passing hour," he said.

Lionel Mathieu, the commander of the city's fire department, said his team was waging a "battle against time."

"The fire has not reached all parts (of the building), so there is hope," he said.

The fire at the site has made it hard for the dogs to detect more victims or survivors.