Why are the next few hours important for Uttarkashi rescue operation?

Uttarkashi Tunnel Rescue: Today is the 13th day of the Silkyara Tunnel accident of Uttarkashi. The rescue operation is going on at a fast pace to rescue the 41 laborers trapped in the tunnel. The agar machine involved in this operation is having intermittent malfunctions. There is also news that now the final phase of the rescue operation is going on. The next few hours are considered very important for this campaign. Earlier, Uttarakhand CM Pushkar Singh Dhami said that the rescue operation is in the final stages. the team trying to rescue the workers has reached very close.