The death toll from Wednesday's flash floods along the Nepal-Tibet border has climbed to at least 160, with hundreds still missing, as rescue teams worked through the night and scientists raced to establish the cause.
Toll Climbs As Search Widens
Nepal's prime minister's office deployed 11 ground rescue teams overnight, with airlifts and tunnel rescues planned from Thursday morning.
More than 340 foreign nationals remain unaccounted for, including at least over 100 Indians, prompting Bihar to be placed on alert over downstream impact, while China has mobilised emergency personnel near the border.
A local Red Cross representative said entire villages and market areas had been wiped out.
Landslide, Then Tremors, Say Scientists
Nepal's foreign minister, Shishir Khanal, said an earthquake likely triggered a landslide that dammed a river before it breached, AFP reported.
The US Geological Survey later revised this, saying seismic analysis showed the shaking, initially recorded as a magnitude 4.4 earthquake, was in fact generated by the landslide itself.
Satellite imagery reviewed by ABC News supported this, pointing to a large glacier chunk breaking off and tumbling into the river.
International Centre for Integrated Mountain Development (ICIMOD) found no anomalies on the Chinese side of the border; remote sensing analyst Sarthak Shrestha told AFP the team believed a rock-ice avalanche in Nepal blocked the Lhende river.
Rijan Bhakta Kayastha, a professor at Kathmandu University and climate researcher, said a preliminary assessment based on discussions with scientists in Nepal and China suggests an ice avalanche fell into and blocked the Lhende river, causing water to build up before bursting downstream into the Bhotekoshi, the Kathmandu Post reported.
"There is information that an ice avalanche from the Nepal side blocked the Lhende river," Kayastha said.
ALSO READ: '109 Indians Missing': Flood Wreaks Havoc In Nepal, Death Toll Mounts To Eight
'Running Won't Help,' Warn Experts
Hydrologist Hatim Sharif of the University of Texas at San Antonio told AFP the lack of rainfall beforehand undermined every conventional flood-warning system.
He said fleeing was futile once such a flood hit, since the fast-moving mud behaves like liquid concrete; climbing at least six metres uphill was the only viable option.
Real-time river-level gauges could offer 20-30 minutes of warning in future, he added. Dorothy Heinrich of the University of Reading said the Himalayas' narrow channels cause any blockage to build up water rapidly before releasing it with extreme speed.
ICIMOD's Qianggong Zhang warned of a possible second flood given an ongoing blockage upstream.
ALSO READ: Nepal Flash Floods Updates: Death Toll Rises To 95, Up To 500 Missing
Climate Change Questions Remain Open
Nepal remains prone to glacial lake outburst floods, a hazard blamed for a similar 2025 disaster that began in China's Gyirong county, though officials haven't confirmed one occurred here.
Scientists plan attribution studies to assess how far glacial retreat and permafrost loss contributed, though Heinrich cautioned a firm link requires such a study to confirm it.
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