Eight climbers feared to have died on Nanda Devi took an untested route without permission and retrieving their bodies will be a high-risk operation, officials said today.
Five bodies have been spotted on the slopes of the country's second highest mountain, but rescuers say it could take days to get them down.
British climber Martin Moran led three other Britons, two Americans, an Australian and an Indian on the expedition that officials said had permission to scale Nanda Devi's eastern peak.
But Moran's expedition company announced on Facebook on May 22 after reaching a second base camp that they planned to attempt "an unclimbed peak" 6,477 metres high.
"This mountain range is more difficult to scale than Mount Everest. They knowingly risked their lives after changing their plans without informing the authorities," an official involved in the operation told AFP on condition of anonymity.
"The permission was granted for Nanda Devi east, and any diversion is illegal. We were completely unaware of their changed plan and that turned fatal," he said.
Authorities will have to organise "a very high-risk and high-altitude operation" to retrieve the bodies, Vivek Kumar Pandey, a spokesman for the Indo-Tibetan Border Police, told news agency AFP.
High Altitude Fall
"In recent times such a high-altitude retrieval has not been carried out in Indian mountains," he added.
The district administration has asked for military assistance in getting to the bodies in a zone with a high risk of more avalanches, Pandey said.
"Trying to reach there on foot could be very risky as there are crevasses and it will take longer than usual."
Aerial pictures shot on Monday showed four bodies together and another buried at a distance on a ridge that was swept by an avalanche. Three more were believed to be nearby.
A military source said the climbers may have fallen from an ice ridge or an overhanging mass of snow during the avalanches.
"There must have been some error of judgement and they must have fallen from a great height along with the entire snow cornice. It must have been like falling from a 10-storey building," the source told AFP.
"They took a different route for which they didn't have permission. It is their adventurism which cost them their lives," the source said.
Surendar S Panwar from local trekking operator Cosmos Tour and Expedition, said the much-respected Moran had already climbed other peaks in the area.
"It is quite surprising how a qualified mountaineer like him made a mistake," Panwar told AFP.
Officials said 12 climbers had set out from Munsiyari in Pithoragarh but they separated into two groups a week later after reaching the Nanda Devi east base camp.
The groups communicated last on May 26, a day before heavy snow fell and massive avalanches hit the heights.
When the eight failed to report back to the base camp, the other four launched their own search before alerting Indian authorities who started their own massive hunt.
Hundreds of climbers from across the world visit India to scale mountains across the Himalayan chain, and the peaks in Nanda Devi sanctuary are considered among the toughest.
The first successful ascent of Nanda Devi was in 1936.
India has 10 peaks above 7,000 metres, including Kangchenjunga - the world's third highest - between India and Nepal.
The latest deaths come a week after the end of a deadly climbing season on Mount Everest where 11 people died, amidst criticism of authorities for allowing record numbers onto the slope.