The Indian army said on Wednesday that 23 soldiers were missing after a powerful flash flood caused by intense rainfall tore through a remote valley in the mountainous northeast Sikkim state. “Due to sudden cloud burst over Lhonak Lake in North Sikkim, a flash flood occurred in the Teesta River 23 personnel have been reported missing and some vehicles are reported submerged under the slush,” the army said in a statement. “Search operations are underway.” The remote area lies close to India’s border with Nepal, and Lhonak Lake sits at the base of a glacier in the snowy peaks that surround Kangchenjunga, the world’s third-highest mountain. The army said water released upstream from the Chungthang dam meant the river was already more than 4.5 metres (15 feet) higher than usual. A video released by an Indian army spokesman showed a thick torrent of raging brown water sweeping down a thickly forested valley, with roads washed away and power lines ripped down. Flash floods are common during the monsoon season, which begins in June and normally withdraws from the Indian subcontinent by the end of September. By October, the heaviest of the monsoon rains are usually over. Experts say climate change is increasing their frequency and severity.