NHPC’s own 2024 paper recorded gas fires in Teesta-VI tunnels before fatal blast

A fatal blast occurred at the Teesta Stage-VI hydroelectric project in Sikkim, killing at least 15 workers. An internal paper by NHPC engineers from 2024 had previously recorded repeated encounters with flammable gas, including methane, and gas fires in the project's headrace tunnels, attributing it to fractured Himalayan rock in Seismic Zone IV. The project, initially developed by Lanco Teesta Hydropower Limited and later acquired by NHPC, faced extensive geological instability and construction challenges. NHPC stated measures were in place to prevent explosions and is investigating the incident, while the Sikkim government has formed a SIT. The project had received environmental and forest clearances between 2006-2021.