KATHMANDU, Nepal, Aug 30, 2026 (AFP) - Nepali rescuers seeking to reach hydropower workers believed trapped in tunnels swamped by flood debris were hampered Sunday by heavy overnight rain and rising river waters.

Nepal's government says more than 100 workers may still be alive and trapped inside multiple tunnels at hydropower projects, with key rescue efforts focused on the Trishuli 3A and 3B sites.

They are among 933 hydropower workers missing since a wall of mud and debris swept down on Wednesday morning, according to the National Disaster Risk Reduction and Management Authority.

At Trishuli 3A, army rescue teams using drills broke through Saturday evening into the upper part of a mud-swamped tunnel and began pumping air and sending a camera inside.

But overnight rain and rising river waters hampered efforts at that site.

"Heavy rainfall after around 2:00 am (2015 GMT) caused the water level in the river to rise, and also fill in the excavation area," the Nepal Army said Sunday morning, as rescue efforts entered their fifth day.

Photographs shared by the disaster office showed workers wading through churned mud and navigating vast boulders left by the floods.

Nepal's prime minster's office said that teams faced "continuous rainfall and difficult conditions" but had worked nonstop overnight "making tireless efforts to search for and rescue those who may be trapped."

The rescue teams are using advanced search cameras and specialised monitors, it added.

The US Geological Survey said the disaster on the China-Nepal border was caused by a glacial collapse.

Specialised Indian and Chinese tunnel-rescue teams have also joined the efforts.

Nepal's expert mountain rescue teams -- used to aid climbers on the world's highest peaks, including Everest -- are also joining the search for missing people at another damaged hydropower site.

The Nepal Electricity Authority said 11 hydropower stations and one solar power station had stopped operating, with a combined capacity of 431.1 megawatts.

That represents about 10 percent of Nepal's installed electricity generation capacity, according to the authority.

Another 15 power projects under construction, with a combined planned capacity of 470 megawatts, have also been damaged.