An explosion ripped off the side of a five-storey residential building in France's Champagne country today, killing at least two people and injuring nine others, officials said.

A search for survivors of the incident is under way.

More than 100 rescue workers, firefighters, sniffer-dog squads and bomb and gas experts were deployed to the gutted building in a subsidised housing complex in the city of Reims, east of Paris, officials said.

Early pictures on the website of a local newspaper, L'Union L'Ardennais, showed heaps of debris spilling out of the building onto a grassy esplanade below, with two helmeted people perched up on a crane for a look inside.

Reims mayor Adeline Hazan told France's BFM television that "a very powerful explosion" had taken place, blowing out windows of nearby buildings.

She said the bodies of the two people killed remained under the rubble. Ms Hazan said the blast had the earmarks of a possible gas explosion but insisted only a thorough investigation would determine the exact cause.

Michel Bernard, the top government official in Reims, told The Associated Press that one person was seriously injured.

He said the building dated to the 1960s and an official investigation was under way to determine the cause. He added that about 10 of the 40 or so apartments in the building were affected.

The precariousness of some buildings has come to light internationally in recent days following the collapse on Wednesday of an eight-storey building in a suburb of Dhaka, Bangladesh, where at least 362 people have been confirmed to have died.

Officials there said three of the floors of that building, which had housed garment factories, had been built illegally.