France is to repatriate the bodies of all 118 people who were aboard an Air Algerie plane that crashed in Mali, as it declared an unofficial three-day period of mourning.

"When it will be possible, all bodies will be brought back to France, all the bodies of all the passengers on the flight," Francois Hollande, the French president, told reporters after meeting with relatives of the victims on Saturday.

France was hit hardest by the crash, with 54 nationals killed.

The jet, which was travelling from Ouagadougou in Burkina Faso to Algiers when it went down in a remote area of Mali, was also carrying passengers and crew from Burkina Faso, Lebanon, Algeria, Spain, Canada, Germany and Luxembourg.

Hollande also said flags on every public building would fly at half-mast for three days from Monday to mourn the air disaster.

The presidency said it was not an official national mourning period, which must be decided at cabinet meetings, but rather a sign of mourning.

Aviation experts search for clues

Meanwhile, aviation experts, criminal investigators and soldiers converged on the crash site to search for clues that might explain why the passenger jet fell from the sky in a storm and apparently disintegrated on impact.

French authorities had said on Friday that the air disaster was probably the result of extreme bad weather but they refused to exclude other possibilities without a full investigation.

Investigators at the scene concluded the McDonnell Douglas MD-83 aircraft broke apart when it smashed into the ground early on Thursday, officials said, suggesting this meant it was unlikely to have been the victim of an attack.

"French soldiers who are on the ground have started the first investigations," French President Francois Hollande said. 

The plane was flying from Ouagadougou, capital of Burkina Faso, to Algiers, Algeria, when it disappeared just 50 minutes after take-off.

United Nations experts found the second of the plane's two "black boxes" - flight data and cockpit voice recorders - at the crash site on Saturday. The first was found on Friday and sent to Gao, the northern Malian city where a contingent of French troops is based.

Source: Agencies