Three French sports stars were among the 10 people killed in a crash Monday involving two helicopters in Argentina, French President Francois Hollande’s office confirmed Tuesday. The cause of the accident, which claimed the lives of eight French nationals and their two Argentine pilots, is reportedly unknown.

"The sudden death of our fellow French nationals is a cause of immense sadness," said a statement from Hollande, BBC reported.

France's Olympic gold medal swimmer Camille Muffat, Olympic boxer Alexis Vastine and sailor Florence Arthaud died in the crash that occurred near Villa Castelli in La Rioja province, about 730 miles northwest of Buenos Aires. The sports figures were involved in the filming of popular European reality show “Dropped.” On Sunday, the crew had arrived in Villa Castelli, where it had previously filmed a version of the show for Switzerland and Denmark, Andres Navarrete, Villa Castelli's mayor, said, according to The Associated Press (AP).

"An explosion occurred and it's believed that they collided," said La Rioja Secretary of Security Cesar Angulo, according to AP.

The pilots, who died in the fatal crash, had been identified as Juan Carlos Castillo and Roberto Abate, AP reported. "The helicopter from La Rioja was a Eurocopter with a capacity to hold six people. It appears to have brushed against the other helicopter from Santiago del Estero shortly after takeoff," the statement from the provincial government reportedly said.

"We learn with great sadness about the accident during the filming of the Dropped show," a statement from channel TF1, which airs the show, said, according to the BBC, adding: "All TF1 teams come together in this terrible time with the pain of the families and relatives of the victims."