The chances that any of the eight climbers missing after trying to scale an unconquered peak in the remote Indian Himalayas are still alive are virtually nonexistent, an Indian official told NBC News on Tuesday.

Vivek Pandey with the Indo-Tibetan Border Police Force, which is helping with the search, said an air-based operation is being launched to retrieve the bodies of the climbers, all of whom are now presumed dead.

Pandey said it was determined that it was not possible for rescuers to get to the climbers by land.

“It is better to go by helicopter to retrieve the remains,” he told NBC News.

Pandey said they are “almost sure” that the climbers didn’t survive.

“But until we don’t go physically, we don’t know,” he said. “But at that altitude, and with this amount of time, the chances of survival are pretty much nonexistent.”

On Monday, officials told NBC News that air force helicopters were out looking for the climbers. Searchers were able to take photographs of the area where an avalanche hit, in which at least five bodies could be spotted.

Vijay Kumar Jogdande, a deputy commissioner in Pithoragarh, the authority in charge of this case, said they believe that the bodies found must belong to the same group of climbers that was reported missing Friday, although he added that the aerial footage obtained by rescue crews didn’t allow them to confirm any identities.

“The terrain in which we have found the bodies is very difficult, considering the fact that it is at an elevation of 5,000 meters (3.1 miles) above sea level,” Jogdande said.

Although search crews want to retrieve the bodies as soon as possible, he said weather conditions were not favorable and any fresh snowfall could make the bodies irretrievable, adding that helicopter pilots spotted 20 to 25 avalanches during their approach to the site Monday.

The rescue effort for the climbers — four from Britain, two from the United States, and one each from Australia and India — began Saturday when they did not return to their base camp the previous day.

It's believed the group disappeared after setting out to attempt an unclimbed, unnamed peak in the Nanda Devi region of the mountain range.

It was led by Martin Moran, the founder of a Scottish adventuring company, Mountain Moran.

In a statement on its website, the company said it was not clear what exactly happened to the climbers, but the alarm was raised when another British mountain guide, who was leading a separate trekking group as part of the same expedition, was informed that the climbers had not returned to base camp as expected.

He then immediately went on the mountain to search for the missing mountaineers, the company said, and saw “clear evidence that a sizable avalanche had occurred on the mountain and it seemed to be on or very near the route that would be taken by the climbing group.”

The U.S. Department of State said Sunday that it was aware of reports that two American citizens were missing in India. NBC News has reached out to the American embassy in New Delhi for further comment.

But Indian officials have now identified the two missing American climbers as Anthony Sudekum and Ronald Beimel.

Sudekum, 63, is a medical doctor from Defiance, Missouri.

On Monday, his daughter, Lucy Sudekum, said she and her family were hopeful that her father would be found alive.

“Our hope and optimism in this dark moment is buoyed by the knowledge that our dad was a highly experienced climber and outdoorsman and an accomplished medical doctor well trained in emergency medical care,” she said in a statement to NBC News.

Anthony Sudekum, second left, is missing in the Indian Himalayas.

“There are countless stories in mountaineering history of avalanche survivors, presumed dead, turning up alive days later in an unexpected location. That is our hope and we are holding onto that now,” she added.

The district magistrate's office in the area has identified the other missing climbers as Martin Moran, John Mclaren, Rupert Whewell and Richard Payne (all from Britain), Ruth McCance from Australia and Chetan Pandey of the Indian Mountaineering Foundation. Moran was the expedition leader and Pandey the liaison officer.

Wing Commander Amit Chowdhury with the Indian Mountaineering Foundation said Pandey was an exceptionally competent mountaineer.

“He has been climbing in India for several years. Martin had requested Chetan to climb with him for several years,” Chowdhury said, adding that Moran was himself a very accomplished and respected mountaineer who has been coming to the Indian Himalayas for many years.

Australian officials told NBC News on Tuesday they are providing consular assistance to the family of the Australian woman who is known to have been part of the group.

The British High Commission also confirmed that their staff is supporting the families of the British nationals reported missing, and is in contact with the Indian authorities.

The group's disappearance comes amid this season's high death toll on Mount Everest. Inexperienced climbers and overcrowding on the world's highest mountain are being blamed for the deaths, with the toll reaching at least 11 last month.