Drone pilot Manish Maharjan has assisted rescue teams in Nepal in locating individuals who went missing following last week’s catastrophic floods, at times employing speakers mounted on the devices to call out to or play music for those stranded on hillsides.

However, the effort to find the hundreds of workers presumed to be stuck in the power plant's tunnels—now the main focus of rescue operations—presents a fundamentally different challenge, he said.

“We discovered the tunnels were packed with mud, much like toothpaste squeezed from a tube,” Maharjan remarked.

“There was no hollow or vacant space within.”

Maharjan, who is also a filmmaker, joined the Nepal Army’s rescue efforts a day after the Aug. 26 flash floods, which have killed more than 1,000 people and left thousands missing in Nepal and Tibet.

“We employed loudspeakers to hail them.

In certain areas, we even broadcast music and then paused for a reply,” Maharjan said.

“This proved effective in several instances and enabled us to pinpoint their whereabouts.”

The torrent of water released by a glacial collapse caused extensive damage to critical infrastructure, including roads, buildings, bridges, and hydropower plants — the latest sign of the growing risks in the rapidly warming Himalayas.

At least 900 workers are still missing from 12 hydropower projects buried under mud and debris, and about 500 of them are believed to be trapped inside power plant tunnels.

According to Mohan Kumar Dangi, president of the Independent Power Producers’ Association, some workers in the tunnels managed to raise the alarm when the disaster struck.

However, it remains uncertain whether rescuers have established any contact with the trapped workers since those initial distress calls.

As time elapses, the search for these missing individuals becomes increasingly arduous for rescue teams.

Maharjan, who has been operating thermal drones in the tunnels, said the searches were challenging because of their difficult access and the absence of any empty space.

"Operating drones is only feasible in tunnels that are long and straight," he said.

"Once bends, turns, or zigzags are introduced, maneuvering and conducting an effective search become considerably more difficult."

At the Rasuwagadhi hydropower project on Monday, Maharjan managed to deploy a drone to probe deep into the tunnel and traverse its full length, yet found no trace of any life.

"We inspected it repeatedly, yet it remained clogged with mud and debris," he said.

"Gazing upon it, I could scarcely fathom the sheer force of the flood."