Pakistan, July 21 -- At least nine people have died and 15 others remain trapped after a tunnel collapse at an under-construction hydroelectric project in India's northeastern state of Sikkim, officials said on Tuesday.

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The incident occurred on Monday at a tunnel being built for a state-run hydropower project along the Teesta River in the Himalayan region. Rescue teams have been working to reach workers believed to be trapped deep inside the collapsed structure.

Rajiv Roka, director of the Sikkim State Disaster Management Authority, said authorities estimated that around 25 to 27 people were inside the tunnel when the collapse occurred. Nine bodies hav...