Rescuers struggled on Aug. 31 through mud and debris for a sixth day, as the number of missing people soared to nearly 5,000 since tsunami-like glacial floods roared down from the China-Nepal border, creating an “unimaginable” disaster.

More than 1,400 people are missing, including trekkers in the Himalayas and scores of Hindu pilgrims to Tibet's sacred snow-capped Mount Kailash.

Rescuers were battling through mud even as the threat of new floods loomed, with emergency teams recovering 586 bodies so far and some of the dead swept downstream as far away as…