Drone pilot Manish Maharjan helps rescue teams in Nepal.

They look for people missing after last week's floods.

He used speakers on the drones.

He called out or played music for people on hillsides.

But the search for workers in power plant tunnels is hard.

Many workers are believed to be trapped there.

Maharjan said the tunnels were full of mud.

It was like toothpaste in a tube.

There was no empty space inside.

He joined the Nepal Army's rescue efforts one day after the floods.

The floods came on Aug. 26.

They killed more than 1,000 people.

Many people are missing in Nepal and Tibet.

The floods came from a glacial collapse.

They damaged roads, buildings, bridges, and hydropower plants.

At least 900 workers are missing from 12 hydropower projects.

Mud and debris cover them.

About 500 workers are believed to be inside tunnels.

Some workers called for help when the disaster came.

Mohan Kumar Dangi said this.

He is the president of the Independent Power Producers' Association.

It is not clear if rescuers have talked to them since.

Maharjan flies thermal drones in the tunnels.

He said searches are hard.

The way in is difficult.

There is no empty space.

He can only fly drones in long, straight tunnels.

Bends or zigzags make it much harder.

At the Rasuwagadhi hydropower project, he sent a drone to the end of a tunnel.

He found no sign of life.

He said it was full of mud and debris.

He could only imagine the force of the flood.