Rescue efforts to reach hydropower workers believed trapped alive in tunnels in Nepal have been disrupted by overnight heavy rain and rising river water. The government said more than 100 workers may remain alive in several tunnels at hydropower projects, while operations have been intensified around the Trishuli-3A and Trishuli-3B project areas. Since mud and debris flows began on Wednesday morning, 933 hydropower workers have been reported missing.

At the Trishuli-3A project, an army rescue team reached the upper section of a tunnel buried in mud on Saturday evening using drilling equipment. The team began pumping air into the tunnel and sending in cameras. Nepal Army said on Sunday morning that, after 2 a.m. local time, heavy rainfall raised river levels and flooded the excavated area on the fifth day of the operation.

The Prime Minister’s Office said rescuers faced continuous rain and difficult conditions but worked through the night to locate and rescue people who may be inside the tunnels. Specialist tunnel rescue teams from India and China have joined the operation. Eleven hydropower plants and one solar plant, with combined capacity of 431.1 megawatts, have stopped operating.