More than 300 rescuers are drilling through hard rock and dirt in an attempt to reach a dozen workers trapped underground in Lam Dong Province.
It has been two days since the tunnel at the Da Dang-Da Chomo Hydropower Plant collapsed, trapping 12 workers, including a woman, stuck inside.
On Friday morning, Deputy Minister of Construction Le Quang Hung, who was charged with overseeing the site rescue said a drill that pierced had reached the collapsed section.
He said the drilling work is going smoothly, and rescuers will continue to dig two small tunnels from left and right side to reached the trapped workers.
Rescuers will use explosives to blast through the obstruction.
Deputy Prime Minister Hoang Trung Hai, who arrived at the scene on Thursday afternoon, said it may take three more days to rescue all the workers.
Workers began digging three small tunnels (from the left, the right and above the collapsed tunnel) and reinforced the site with tree trunks on Tuesday.
They also drilled a hole 3 centimeters in diameter through which they managed to insert a plastic tube to provide the trapped workers with milk and congee, as well as another hole to extract water from the collapsed section.
On Thursday morning, they announced that a drill had extracted a large quantity of water from the tunnel, reducing the risk of flooding.
According to the workers, their health is stable despite signs of fever and a reduction in body temperature.
More advanced drilling devices are being rushed to the site to assist the rescue crew.
A group of doctors from Cho Ray Hospital in Ho Chi Minh City has been dispatched to the scene to monitor rescue workers and be ready to provide emergency care to the workers as soon as they're unearthed.
A section of the mountain tunnel caved in 500 meters from its entrance after work began on the Da Dang-Da Chomo Hydropower Plant at 7AM on Tuesday.
Twenty workers managed to run out of the tunnel. Twelve others were trapped inside.