NEW DELHI: At least nine people have died and 15 others remained trapped after a tunnel collapsed at an under-construction hydroelectric project in India's remote northeast, officials said Tuesday (Jul 21). The incident occurred Monday in the Himalayan state of Sikkim, where workers were constructing a tunnel for a state-run hydropower project on the Teesta river. "We are estimating around 25-27 people were trapped," Rajiv Roka, director of the Sikkim State Disaster Management Authority, told AFP. Toxic methane gas leaking from underground rock formations was hampering rescue efforts, officials said, allowing only teams carrying oxygen equipment to enter. In 2023, 41 workers were rescued after 17 days being trapped under a Himalayan road tunnel that had collapsed in northern Uttarakhand state.