The water level in the Dhauliganga river surged again briefly on Thursday, forcing rescue workers to stop for some time their operation to reach the over 30 people trapped in the Tapovan hydel project tunnel after the flash flood four days ago.

The interruption took place amid a massive effort by multi-agency rescuers to break through the sludge and debris that choked the tunnel after Sunday’s disaster, which left 35 dead and about 170 missing.