Indian officials have warned that the chances of survival for eight people believed to have been trapped in a collapsed tunnel for several days are remote, after a rush of silt and water caused the ceiling to cave in over the weekend.

       The group was working on the Srisailam Left Bank Canal tunnel project in the southern Indian state of Telangana, a decades-long effort to build one of the world’s longest irrigation tunnels, which has been plagued by a series of delays since construction began in 2005.

       The workers were about nine miles inside the tunnel on Saturday morning when the roof collapsed after a rush of silt and water, according to local officials and news reports. Some escaped, but eight were left trapped behind a tunnel-boring machine that blocked their exit.

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