Debasish Ghosh is frantic. “We have no information," he said. "In fact, we are the ones who are continuously asking for information. We are sitting at home, numb and restless, waiting for any kind of news..."

The wait has been a long and painful one for Debasish, whose brother, Goutam Ghosh, an assistant sub-inspector in the Kolkata Police, went missing on the weekend during an expedition to Mount Everest.

Ghosh, a Barrackpore resident, and three others – Subhas Paul from Bankura, Sunita Hazra from Kolkata and Paresh Nath from Durgapur – set off last week on the attempt to scale the the world's highest peak.

It isn't clear exactly what happened but the situation took a turn for the worse sometime between Saturday and Sunday, when the group was reported missing as they neared the summit. Paul and Hazra were found, but Paul died on Sunday while he was being taken down to the base camp. Hazra is recuperating at a hospital in Kathmandu.

Ghosh and Nath remain untraceable. Rescue efforts are underway, but chances of their being found alive appear increasingly bleak.

Hazra gave a brief account of her ordeal to Bengali newspaper Anandabazar Patrika. "After descending from the summit, I realised that my head was spinning," she said. "I was taking deep breaths with every step I took and my oxygen was depleting. I lost track of time, the only thought I had was that I had to keep on going. I must have stopped and fallen somewhere... I don't remember."

Here are brief portraits of the expedition members.

Goutam Ghosh: The sub-inspector who dared

Ghosh is a well-known figure in the Bengal mountaineering community and had climbed several peaks over the last two decades. His fellow-mountaineers said that he had completed a course from the Nehru Institute of Mountaineering in Uttarakhand. He had participated in several expeditions and had even attempted to scale Mount Everest before, though those missions were not successful. Never one to shy away from an adventure, he undertook a month-long cycling trip last year from Kolkata to Bangladesh.

“This is a black day for us,” said a visibly sombre Mrinal Chatterjee, the secretary of the East Zone Committee of the Indian Mountaineering Foundation. “I have known Goutam for a long time. He is a known face in the mountaineering circuit. He was not a novice; this was his fifth attempt at mounting Everest. This is incredibly tragic and I can only hope it results in some sort of wake-up call" regarding safety issues facing climbers.

Paresh Nath: Driven by 'mad zeal'

In Durgapur, the news of Nath's disappearance has cast a pall of gloom. The 58-year-old has a wife and son and comes from a modest background. He lost a part of his left wrist in a fire-cracker explosion when he was just 11. He has a small tailoring shop where he stitches mountaineering equipment and also ran a popular Facebook page providing details of his adventures.

"Nath had a mad zeal – he wanted to prove to the world that despite losing part of his arm, he could still traverse the toughest of terrain," said Sagarmoy Chowdhury, the secretary of the Durgapur Mountaineering Association. "He's served as an example to many young mountaineers. They were motivated and felt that if a man like Nath could pull off such incredible achievements, why can't we?"

Subhas Paul: Could do anything for Everest dream

A resident of Bankura, Paul drove an auto-rickshaw for a living but always aspired for loftier goals. To realise his dream of climbing the highest mountain in the world, he had tapped into Facebook to invite sponsors. This was his second attempt to climb the Everest, after his trip last year was interrupted by the Nepal earthquake.

"We could not deter him," said Piyush Chakraborty, Paul's friend from his hometown. "We tried to, when he was thinking about making his first attempt. But even after it proved unsuccessful, his enthusiasm did not diminish. He would tell us that he was even willing to mortgage himself and his house to climb Mount Everest. So when he was thinking of making his second attempt, we encouraged him. And now, it is tragic to think he's not with us anymore."

Sunita Hazra: A veteran of mountain-climbing

For Hazra, this was her third attempt at climbing the mighty Everest – and each of them proved death-defying. In 2014, she was stopped by an avalanche at the Khumbu Icefall that killed 16 sherpas. A year later, Hazra managed to save herself from avalanches triggered by a massive earthquake in Nepal by hiding behind a large rock.

Hazra had taken a break from the mountains a few years ago, but she had made a comeback, according to Pradip Kumar Hazra, secretary of the Himalayan Association in Kolkata. "Sunita is highly qualified and has summitted many peaks," he said. "She is a veteran in the mountain climbing community."

A big challenge

At 8,850 metres, the threat of acute altitude sickness – apart from the extreme weather and challenging terrain – poses many hazards to climbers, even the most experienced ones. "Earlier, to climb the mountain, one would have to train actively and vigorously, take many permissions, vet agencies and verify them," said Basanta Singha Roy, one of West Bengal's most experienced mountaineers. "The procedure is a little easier now, but it still remains one of the toughest climbs in the world. The conditions can be unbelievably difficult for a human body."

Paul is third mountaineer who died on the Everest this weekend – four mountaineers have died in as many days.