The Olympic flame mountaineers set off on their climb up Everest in the early hours to avoid being stranded at the summit once their mission was accomplished, a prominent climber said. The group of 19 climbers left their base camp at 8,300 metres at 3am on the final section of their trek to the roof of the world, a spokesman for the climbing team confirmed. It took at least six hours before the climbers reached the peak and carried out a mini torch relay of their own on the summit. The early-morning arrangement raised further questions about the secrecy that has shrouded the torch's Himalayan journey. The details of the carefully choreographed ascent were kept under wraps and not divulged until the very last minute. Seasoned mainland mountaineer Zhou Xingkang said that getting to the top was far from the end of a successful expedition. 'The downhill route is as painstaking as the ascent and takes as much time,' he told the Beijing News. Mr Zhou, who climbed Everest in 2003, said the temperature usually plunged in the afternoon in the Himalayas, especially atop Everest, prompting most climbers to time their ascent for the morning, and this meant a pre-dawn departure. 'For a summit mission, completing the ascent is just half the battle. You could not claim success until every climber had returned to the base camp safely,' he said. All climbers descended to 6,400 metres yesterday, according to China Central Television, and were expected to go down to 5,200 metres to the biggest of the team's Everest stations today. Groups of foreign mountaineers have been waiting for days - even weeks - for a climbing ban to be lifted. Climbing companies usually charge US$35,000 to US$80,000 per person to reach the summit.