Oxygen, water and food are being given to the survivors through holes dug by rescue workers.
The 170-hour long ordeal for the three workers trapped inside an under-construction tunnel, which collapsed on September 12, is expected to be over in a few hours as the drilling process is nearing its completion.
"Massive round the clock rescue operations are on and 38 meters drilling of horizontal tunnel to reach the trapped employees has been completed, while four to five meters of remaining drill will be done in next few hours," Special Secretary (Disaster Management and Revenue), D D Sharma told the Press Trust of India.
"A fifty-member team of NDRF, specialised in such operations, is all set to take the trapped employees out through the horizontal tunnel. The decision to rescue two of the three employees would be taken after the breakthrough is achieved," he said.
The employees were trapped inside tunnel No 4 of Kiratpur-Nerchowk four-lane project near Bilaspur in Himachal Pradesh on September 12.
He also said that the NDRF officials will conduct a mock drill before rescuing the employees.
The operation was highly technical and experts from National Authority of India (NHAI), Sutlej Jal Vidyut Nigam and HP Power Corporation, are on the job.
Heavy drilling is being carried out with the use of equipment brought from Mathura by Himalayan Construction Company to speed up the process at the rough and rocky terrain, he said.
The horizontal tunnel has diameter of 1-mt, which is sufficient for the rescuers to enter the spot and pull out the trapped persons - Satish Tomar and Mani Ram - employees of Himalayan Construction Company, he said.
Two of the three trapped labourers had been confirmed to be alive as the rescue teams established contact through digital camera and microphone after hours of digging. However, there has been no communication established with the third employee - Hriday Ram - trapped in the debris, and his condition remains unknown.
The trapped persons are in good state of health and water, juices and food is being supplied to them at regular intervals, said Manish Sahay Thakur, Deputy Commissioner, Bilaspur.