Calcutta, March 29: An Indian mountaineer has been missing in the Andes since Wednesday, prompting friends from his alma mater IIM Calcutta and IIT Kharagpur to pool in money for a private helicopter rescue if the South American governments give up.

Andhra Pradesh native Malli Mastan Babu, 40, who conquered the highest peak of each continent (Seven Summits) in an Indian record 172 days in 2006, is lost somewhere along the Argentina-Chile border.

His friends in India said Babu had set out from Argentina with a group of mountaineers on March 22 and reached base camp on the 6,749m Cerro Tres Cruces Sur peak on the Chile border on March 24.

He then made it solo towards the summit, part of the "Tres Cruces" or "Three Crosses" of the Andes, and was to return to base camp the next day. He didn't.

Babu's expedition, which he had started amid rain, required him to find his way through snowfields, a rocky labyrinth, fissure systems and shaky ashlars - a terrain that mountaineers say can pose a stiff challenge in bad weather.

An impromptu search was organised straightaway but was unsuccessful. Rescue operations in the next two days were hit by torrential rain that Chile's deputy interior minister, Mahmud Aleuy, has dubbed the "worst rain disaster to fall on the north in 80 years".

"We have created a Facebook community called 'Rescue Malli Mastan Babu'," said Saurabh Uboweja, a Delhi businessman who was Babu's junior at IIM Calcutta when the budding climber was doing his MBA in 2002-04.

"We have also got together a WhatsApp group, where we have received pledges to the tune of $45,000 if the need arises."

He added: "We have been in touch with Chilean authorities through the Indian embassy for the past few days to start a search with choppers. Because of the flood situation, they were not able to provide choppers but have promised one by Sunday morning (March 29 night by Indian time)."

The funds have been pledged mostly by Babu's former classmates from four institutions: IIM Calcutta, IIT Kharagpur (where he did his MTech in electronics in 1998), NIT Jamshedpur (BTech in electrical engineering in 1996), and the Sainik School at Korukonda, Andhra.

Babu, whose website says "'Never give up, never give in' works miracles for me", is the youngest of five brothers and sisters.

One of his older sisters, Malli Dorasanamma, a neurologist who lives in Tirupati, said she had last spoken to him on March 21, the Telugu New Year's Day, and that "he was to board the flight home from Argentina on Saturday".

"It was not clear if the Chilean authorities would be able to provide choppers at all. That's why the fund collection started. About $5,000 has been sent to a private agency (in Argentina) that has been organising rescue operations on foot," she said.

A friend of Babu in Argentina said a day's rent for a private chopper is $40,000.

The Facebook community page created to aid the rescue has been providing regular updates. A message posted Saturday night (Brazil time) said the private rescue group had reached within 80km of the base camp.

Babu's family has contacted Parliamentary affairs minister Venkaiah Naidu, who like them belongs to Nellore district.

Naidu has spoken to foreign minister Sushma Swaraj seeking her help in nudging Argentina and Chile to speed up the search, the foreign office said this evening.

Sushma has directed ambassadors Amarendra Khatua in Argentina and Debraj Pradhan in Chile to update her on the progress of attempts to trace Babu.

Babu had conquered the Seven Summits between January 19 and July 10 in 2006. To add an extra element to this achievement, he had planned it in such a way that he reached the seven peaks on seven different days of the week.

Debraj Dutta, a mountaineer attached with The Himalayan Club, recalled a presentation Babu had made while delivering the third Sarat Chandra Das Memorial Lecture in Calcutta in December 2007.

"He had just finished a trek of the four dhams - Yamunotri, Gangotri, Kedarnath and Badrinath (through a difficult mountain route and not along the tourist trail) - and took us through the paces," Dutta recalled.

"Hunting for those in the Andes isn't new for Argentina and Chile - they have the expertise and they have a process they follow," a senior diplomat said.

"But we intend to keep nudging them, and to keep getting information back to the family of the missing man."

In February, Chilean mountaineers had found the wreckage of a plane that had crashed in the Andes 54 years ago, with 24 people in it.