Everest filmmaker and mountaineer David Breashears dies aged 68

Mountaineer and adventure filmmaker David Breashears, best known for an IMAX documentary about climbing Mount Everest, has died aged 68.

Breashears was found unresponsive at his home in Massachusetts on Thursday and died of natural causes, said his business manager Ellen Golbranson.

She added that "the exact cause of death remains unknown at this time".

Breashears was an experienced mountaineered who climbed the world's most challenging peaks. As a cinematographer he worked on documentaries and feature films.

According to his website, in 1983, he transmitted the first live television pictures from the summit of Everest, and in 1985 he became the first American to reach the summit twice.

Breashears reached the summit of Mount Everest five times in total, his family said.

"He combined his passion for climbing and photography to become one of the world's most admired adventure filmmakers," they said in a statement.

He is best known for a 1998 IMAX documentary called Everest, which he co-directed and co-produced, about the challenges and struggles of a group of mountaineers trying to reach the peak of the mountain, which at 8,850m (29,035ft) is the world's tallest.

Breashears and his team were filming the documentary in May 1996 when a blizzard struck the mountain, killing eight climbers.

He and his team stopped filming to help the climbers.

In 2007, Breashears founded GlacierWorks, which on Facebook described itself as a non-profit organisation highlighting changes to Himalayan glaciers "through art, science, and adventure".

His family said "he used his climbing and photography experience to create unique records revealing the dramatic effects of climate change on the historic mountain range".