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Three French sports stars were among 10 people killed when two helicopters filming a reality show collided in Argentina on Monday, according to officials.

Adventure Line Productions confirmed the "terrible" accident, saying the collision took place shortly after take off as filming was getting underway on the second season of survival-show "Dropped."

Olympic swimming gold medalist Camille Muffat, long-distance sailor Florence Arthaud and boxing champion Alexis Vastine — "who did so much to shine for France" — were killed along with five other French nationals, the French presidency said in a statement.

"The sudden deaths of our countrymen is a cause of immense sadness," the presidency said in a statement.

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The International Olympic Committee said it was "shocked" by the sad news and would fly the Olympic flag at half-mast for three days at its headquarters.

"The world of sport and the Olympic family have lost three of their key members," it said in a statement. "They were all not only champions in their sport but also contributed greatly as role models."

TF1 — the channel airing the show — said on its website that five members of the production team were killed along with two Argentine pilots of the helicopters. The network expressed its sadness over the accident, saying in a separate statement that it is united with the families of the victims and those close to them at such a painful time.

"We have no details on the exact circumstances at the moment," TF1 chief executive Nonce Paolini later said, according to Reuters. "All I can say at the moment is that we are in a state of complete shock."

Authorities said it was still unclear what caused the accident in the rugged western province of La Rioja near the Andes mountains, according to Reuters. Images from the scene showed large flames, smoldering wreckage and thick black smoke.

Muffat, 25, abruptly retired last summer, partly due to a disagreement with a coach, NBC Sports reported. She won gold in the 2012 Olympic 400m freestyle, silver in the 2012 Olympic 200m free and bronze in the 2013 World Championships 200m free.

France's Camille Muffat poses with her silver medal on the podium after the women's 200m freestyle final during the London 2012 Olympic Games. DAVID GRAY / Reuters, file

Vastine, 28, won an Olympic boxing bronze in 2008. Arthaud, 57, in 1990 secured the record for the fastest solitary crossing of the North Atlantic, according to her publisher's website.

"Dropped" is a popular reality show in France in which eight sports stars are dropped into the wilderness.

Reuters contributed to this report