A flash flood tore through the Nepal-Tibet border region on Wednesday, killing more than 540 people and destroying entire villages, according to survivors and witnesses. Many of those caught were pilgrims heading to Mount Kailash, a sacred site in Tibet.

Laloma, a 27-year-old Nepali mother, said she saw two buses carrying Indian pilgrims swept away by the water. "They are all gone," she said.

Sivaranjani Muthunathan, 46, from the southern Indian state of Tamil Nadu, was traveling by bus with 56 others toward the Chinese border. The group became stuck in what they thought was a traffic jam. "Then there was fog, smoke, something that seemed to suddenly engulf us," she said, showing a phone video of a torrent surging toward her. She said the passengers climbed out through the driver's side as vehicles were swept away or buried.