More than 1,300 people have died and thousands are missing, but rescuers' hopes have risen after finding survivors in a tunnel.

At least 639 people remain stranded in devastated hydropower stations that have become ⁠the focus of rescue ⁠efforts, Nepal's disaster management authority said on Tuesday. The death toll rose to 1,050, while about 4,000 people remain ​missing, including 583 foreign nationals.

An Australian engineer advising the effort described how two men were freed after nine days trapped in a tunnel at the Upper Trishuli 3A hydropower plant.

The devastating flood in Nepal last week could ​result in commercial insurance losses exceeding 20 billion Nepali rupees ($132.3 million), with hydropower projects accounting for most claims, ‌according to a top official at one of the country's leading insurers.

A Toronto woman whose relative is among the missing, said family members have been left scouring the internet, looking on Nepal police sites and missing identity sites to see if the names of any relatives come up.

Rescuers were racing on Friday to find more survivors among dozens of people believed to be trapped in a tunnel at a hydropower project, officials said. It was not clear how many were still alive.

Some survivors in Nepal's relief camps after deadly floods are struggling to obtain essential medicines and cash.

An additional 4,216 people were believed to still be missing, officials said.

As the planet warms, glacier meltwater and a thawing permafrost could have contributed to destabilizing the rock.