India, Sept. 4 -- A WhatsApp group created by engineers just before disaster struck Nepal's Trishuli valley is now helping rescuers navigate tunnels buried under tonnes of mud, rocks and debris. The group reportedly has more than 500 members, including engineers, former hydropower employees, government officials and other experts.

The August 26 disaster sent a massive wall of water, mud and rocks down the valley following a glacial and mountain collapse near the Nepal-China (Tibet) border. At least 1,287 people have died, according to official records, while nearly 4,000 remain missing.

With search teams racing against time, the engineers' group has emerged as an unlikely lifeline, providing rescuers with crucial information about burie...