Kathmandu. Catastrophic flooding and landslides on the Nepal-Tibet border unleashed waves of water and debris on Wednesday that killed more than 360 people and left more than 1,400 missing.

The figures are likely to change, which is not uncommon after a major disaster.

Double-counting of dual nationals, matching bodies with people listed as missing, and the chaos of a calamity can all contribute to fluctuations both upwards and downwards in the figures.

The exact sequence of events is still unclear, but on that morning, a tsunami-like wall of freezing water and mud wiped out towns under a torrent of sludge, engulfing homes, smashing bridges and dams, and sweeping vehicles away like toys on both sides of the border.

It gouged a path nearly 170 kilometres (105 miles) through Nepal, experts said, hitting villages and towns on the path of two rivers -- Bhote Koshi and Trishuli.

Surveillance footage from the Chinese side showed a wall of mud and water crashing over a building as terrified people ran.

Emergency teams are racing to pluck survivors from affected zones, while Nepali soldiers used sniffer dogs and heavy equipment to search for bodies buried under the suffocating dirt.

Nepal's disaster agency said 910 people were unaccounted for on Thursday, including at least 517 foreigners. It did not give a breakdown of the nationalities of the foreigners.

Across the border with Tibet, China said 558 people -- including 260 foreigners -- were missing. Together, the total missing on both sides of the border is 1,468.

Nepal's tourism board on Thursday put the number of missing tourists and travellers -- Nepali and foreign -- at 667 in total. 

Possible Cause
While the explanation for the calamity has evolved since it struck, it appears linked to a collapsing glacier.

Within hours of the flooding, Nepal's authorities said an earthquake likely triggered a landslide, in turn blocking a river and sending water gushing downstream.

China also reported a landslide, saying a border hub between Tibet and Nepal had been hit by a surge of debris.

The Nepali authorities' explanation aligned with a US Geological Survey report of a quake in Tibet that was north of the disaster zone.

However, USGS subsequently updated its conclusion to say the seismic activity initially reported as a quake "was instead a glacial collapse and debris flow" that "caused subsequent catastrophic impacts downstream".

"Additional analysis of nearby seismic stations, long period seismic waves, and satellite imagery led to the determination that the seismic event was instead a glacial collapse and debris flow, and that no earthquake had occurred," the agency said.

Fears of more potential floods remain, with water trapped by the immense piles of debris blocking the valley.

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