Rescuers on Monday worked to free hundreds of workers believed to be trapped in tunnels at hydropower projects buried in mud by catastrophic flooding on the Nepal-Tibet border. The combined death toll in Nepal and Tibet has surpassed 950, with more than 4,400 people reported missing.

A private-sector association representing power companies said at least 900 workers were unaccounted for at 12 hydropower projects damaged by the flash floods in Nepal's Rasuwa and Nuwakot districts. About 500 of those workers were believed to be trapped in tunnels.

At least one expert said some workers could have access to oxygen, but others warned that the chances of finding survivors were diminishing. Families of the missing have grown increasingly desperate as the search continued.