Construction of the tunnel at Khuntan, which was cut through solid granitee bedrock, began in 1918. Khuntan tunnel was nicknamed the "cemetery of laborers" as it is said that over 1,000 workers died while constructing the tunnel due to suffocation, accidents, malaria, tigers and fighting amongst themselves. It is said that the workers were opium addicts (how they became addicts is unknown) who agreed to work because they were given opium in addition to the wages.