Hundreds of rescuers are trying to dig through to a collapsed section of tunnel at the Da Dang-Da Chomo Hydropower Plant in the central highlands province of Lang Don to rescue 12 workers trapped since December 16.

 Rescue work underway at the collapsed tunnel

As the rescue operation enters its third day, two narrow conduits have been driven through to the 11 men and one woman trapped inside the tunnel, ensuring they have an air supply and food and water. Rescuers have also managed to begin pumping out rainwater runoff, that rose to 1.4 metres overnight, holding the water level at 30-40 centimetres.

Rescue authorities have decided on a strategy to try to reach the trapped workers from five angles, with three drills working from the entrance of the tunnel, with a fourth attempting to work backwards towards them, and another from a hillside directly above.

But the drills can only move at a rate of 60 centimetres an hour due to the hardness of the rock around the collapse.

 Drilling to the trapped workers

A rescue team from Vietnam National Coal and Mineral Industries Group is attempting to tunnel around the collapsed section, but one team member said progress was slow and the new tunnel would take two-to-three days to break through.

Experts studied but dismissed a plan to use explosives to blast through the debris.

One hundred soldiers are at the rescue sight assisting 300 local police and volunteers, with more rescuers and fire fighters on their way from HCM City to assist in the rescue effort.