How did the tunnel accident happen?

It has been more than 50 hours since the Silkyara Tunnel accident in Uttarkashi, Uttarakhand. But still the lives of 40 laborers are stuck inside the tunnel. From the government to the administration, everything is being done. Now preparations are being made to evacuate the workers with the help of steel pipes in the tunnel. All the machines have reached the spot. The pipes are being put inside. The biggest blessing after 3 days of the accident is that all the workers are safe. We are in constant contact with him. Conversation is being done through walkie-talkie. Oxygen is being supplied to the workers. For the rescue operation, work is being done to remove debris through machines.