Star French athletes killed in helicopter collision while filming reality TV show in Argentina
People are seen near the burning wreckage of two helicopters that collided mid-air near Villa Castelli, in the Argentine province of La Rioja, on March 9, 2015, killing 10 people (AFP)

French sports stars, including an Olympic champion swimmer and one of the world's best sailors, were among 10 killed in a helicopter crash while filming a reality TV show in Argentina.

Champion sailor Florence Arthaud, Olympic gold medallist swimmer Camille Muffat, Olympic boxer Alexis Vastine and seven others died when two helicopters filming the survival series "Dropped" smashed into each other in the rugged mountains of La Rioja province, local officials said.

"Apparently, the two helicopters collided as they were filming. There are no survivors," provincial spokesman Horacio Alarcon told AFP.

He said the weather conditions were good and the cause of the crash, which happened late afternoon local time on Monday, was unknown.

Local media showed the wreckage of the two helicopters in flames on the dry scrubland in the northwestern Argentinian province.

Eight French passengers and their two Argentine pilots died in the crash, a police source said.

'Immense sadness'

Arthaud, 57, was considered one of the best sailors in the world, a woman who conquered what had been a strictly male-dominated sport. Her titles included the 1990 Route du Rhum, the most prestigious race to cross the Atlantic solo.

Muffat, 25, was one of the top swimmers in French history, winning three medals at the London Olympics in 2012, including gold in the 400-meter freestyle.

She shocked the sporting world in June 2014 by announcing her sudden retirement at the age of 24, exhausted by the long hours of training in the pool.

Vastine, 28, won a bronze medal at the Beijing games in 2008 in the light welterweight category.

President Francois Hollande led the tributes, saying the "brutal death of our compatriots is an immense sadness."

"The whole of France is in mourning this morning," said Prime Minister Manuel Valls.

The reality TV show, called "Dropped," involved eight sports stars being dropped into inhospitable environments for an adventure- and survival-themed show.

Fellow contestant, former France and Arsenal football star Sylvain Wiltord, said on Twitter he was "sad" and "horrified."

The other stars participating in the show -- none of them hurt in the accident -- were swimmer Alain Bernard, cyclist Jeannie Longo, snowboarder Anne-Flore Marxer and figure skater Philippe Candeloro.

"We've got people who are way beyond average for their record of achievements, that's clear," said the show's presenter, Louis Bodin, in a recent interview with French radio station RTL.

"And we can tell that on the ground, on all kinds of terrain, that they've got the ability to adapt ... Of course, the logistics, the conditions are sometimes a little complicated," he added of the show that was to air on French television channel TF1.

The provincial government said a cast and crew of around 80 people, mostly French nationals, had descended on the area in recent days to film the series.

Shooting began in late February in Ushuaia, at the southern tip of South America in the glacial terrain of Patagonia.

It then moved to La Rioja, whose scenic mountain landscapes are popular with tourists.

Film crews from the series had already shot preliminary footage in Villa Castelli in late September, said local news site DataRioja.

'Extreme' landscape

The crash happened around 5:00 pm (2000 GMT) near the town of Villa Castelli, about 1,100 kilometers (700 miles) north of the capital Buenos Aires, said provincial security secretary Cesar Angulo.

The provincial government said the crash happened in the Quebrada del Yeso gorge.

One of the helicopters was provided by the provincial government and the other by the police force in the neighboring province of Santiago del Estero.

Police and firefighters were still working to recover the victims' bodies when night fell, using floodlights to illuminate the area, a police source told AFP.

"It's been four hours since the collision and (the wreckage) is still on fire. There's smoke rising from the helicopters," said a police source at the scene.