00:00A catastrophic flash flood has swept through Nepal's Himalayan border region.
00:04Several people have been killed and hundreds are still missing, including tourists,
00:09as rescue teams struggle to reach the worst-hit areas.
00:12But what caused such a sudden and destructive surge of water?
00:16The disaster began high in the Himalayas.
00:18An earthquake is suspected to have triggered a massive ice and rock avalanche into the Linde Kola River.
00:25The debris sent a sudden wall of water, mud and rocks downstream, sweeping away homes, roads, bridges and vital infrastructure.
00:32The surge came with little warning, leaving people with almost no time to escape.
00:37And the danger may not be over.
00:39Nepal has put border areas on high alert, as a blocked lake in China could still cause more flooding.
00:45Rescue teams are searching for the missing, but dangerous conditions are making access difficult.
00:50With hundreds still unaccounted for, the death toll could rise sharply as rescuers reach areas cut off by the floods.
