Scottish based climber among four Brits missing in the Himalayas
Martin Moran and his team were expected back at their based on Friday, but never appeared.
Local media reports say the group were attempting to reach the summit of India's second-highest peak Nanda Devi in Uttarakhand.
The missing Britons have been named locally as group leader Martin Moran, John McLaren, Rupert Whewell and Richard Payne.
US nationals Anthony Sudekum and Ronald Beimel, Australian Ruth McCance, and Indian guide Chetan Pandey are also missing.
The group, led by Mr Moran, a UK-based mountain guide, left their base camp in Munsiyari on 13 May and were due to return on Friday.
A post on the Moran Mountain Facebook page on 22 May said the team had reached their second base camp at 4,870m.
A rescue team was sent out late on Friday night after the mountaineers failed to return to their camp, but rescuers are travelling on foot and are not expected to reach the area until this evening.
Local mountaineers said there had been a heavy avalanche on the group's planned route.
A Foreign Office spokesperson said: "We are in contact with the Indian authorities following reports that a number of British nationals are missing in the Indian Himalayas.
"We will do all we can to assist any British people who need our help."
Nigel Vardy, a mountaineer who has known Mr Moran for 20 years, described his friend as a "top of the range" climber, who "knows the mountains, he knows the area, he knows what he is doing".
Speaking to Sky News, he said the pair had climbed together extensively, and that Mr Moran was at "the top of his game".
But avalanches can catch even the most experienced climbers unawares, Mr Vardy explained.
He noted that experienced mountaineers can make intelligent estimates on routes they know are prone to such incidents, but that sometimes there are just "seconds of notice", which "can be too late".
He added: "Avalanche debris is incredibly heavy. It sets like concrete. You really don't just walk out of this stuff."
This latest incident comes amid a deadly season on the Himalayas, with at least 17 people dying on the mountain range this year.
On Monday, American climber Christopher Kulish became the 11th person to die on Mount Everest in recent weeks.
Kevin Hynes, a 56-year-old from Ireland, died in his tent last month after texting friends to say the expedition was "proving the most fun he had had".
British climber Robin Fisher, 44, died 150m (almost 500ft) below Everest's summit on his descent.
The recent deaths are believed to have been exacerbated by a crowded route to the summit, causing delays, which some have blamed on the number of inexperienced climbers allowed to tackle the mountains.
British climber and former paratrooper Martin Hewitt described the situation as a "free-for-all".
"Ultimately there are a number of people attempting this mountain that do not have the fitness, the experience, the technical skill or the credibility to realistically attempt a mountain like Everest within a relatively safe time frame, and there are bottlenecks on the mountain," he said.
"There are areas where it is not really safe or practical to overtake other people.
"So when you have climbers who are not capable of climbing stuck in these locations, everybody else basically gets stuck behind them."
A record 381 permits were issued to scale Everest for this climbing season.