Rescuers race to free trapped workers in Himalayan tunnel

Rescuers raced to free around 35 Indian construction workers, who were among 197 people who officials said were still unaccounted for as the death toll from the disaster reached 32.

Packing rocks, dirt and construction debris and thought to have been triggered when a glacier lake fed by India's second highest peak, Nanda Devi, collapsed, the flood swept down the Dhauliganga river on Sunday (February 07).

The 520 MW Tapovan project, being built by state firm NTPC, is one of many run-of-river projects being developed to upgrade Uttarakhand's power network.

Officials have yet to conclusively determine what caused the disaster, though scientists investigating it believe heavy snowfall followed by bright sunshine combined with a rise in temperatures may have triggered the glacier's collapse.

A clearer picture of the circumstances is expected to emerge later this week, officials said.