Nepal and China resumed rescue operations that had been suspended briefly in the flood-hit Himalayas on Friday after risks from an overflowing lake were found to be manageable, easing fears of fresh devastation.

A glacier collapse on Wednesday unleashed a huge torrent of rock, ice, mud and debris through Himalayan mountain river systems, killing at least 579 people in Nepal and five in China’s Tibet.

The number of missing persons in Nepal had nearly doubled to 1,924, the country’s disaster authority said on Friday. At least 558 were missing in Tibet’s Gyirong County, including 260 foreign nationals, Chinese state broadcaster CCTV said on Thursday.

More than 90,000 people were estimated to have been affected by the disaster, the Red Cross said.

The flooding led to the formation of a lake, which on Friday began overflowing into the Lhende Khola and Trishuli rivers.

The overflow sparked panic and warnings from authorities in Nepal, leading to rescue o...