Himachal Pradesh Chief Minister Virbhadra Singh on Thursday visited the under-construction road tunnel near here, where three workers have been trapped since September 12, an official said.The chief minister spent more than an hour at the spot and reviewed the ongoing massive rescue operation, involving the Border Roads Organisation (BRO) and the army, a government official told IANS.He said the rescue personnel have managed to established contact with two workers - Mani Ram and Satish Kumar. The whereabouts of the third worker, Hirdya Ram, is still unknown.Three labourers have been trapped since Saturday evening when the under-construction tunnel of Kiratpur-Manali four-lane road project collapsed and blocked the passage, police said.Bilaspur Superintendent of Police Balbir Thakur told IANS that eatables, including dry fruit and glucose, were supplied to the two workers through a pipe inserted inside the tunnel.He said contact was established with two workers through a microphone inserted through the pipe after vertical drilling into the tunnel."Their visuals were caught on a camera and they were responding," he added.Deputy Commissioner Manasi Sahay Thakur said vertical as well as horizontal drilling was underway to reach to the trapped workers."After drilling another 10 to 12 m, we hope to reach those trapped inside," she added.