Nepal issued a fresh warning as water levels in a key river rose, threatening to disrupt rescue efforts after catastrophic flooding killed hundreds and left thousands still missing along its border with China.

Rescue personnel and those providing relief services in regions surrounding the Bhote Koshi river’s path were told to exercise “utmost caution,” the National Disaster Risk Reduction and Management Authority said in a post on X.At least 690 people have been confirmed dead, while over 3,000 are still unaccounted for, according to figures provided by Nepal and China. The death toll is likely to rise as rescue workers speed up efforts to retrieve bodies.

The catastrophe was triggered on Wednesday by a glacial collapse that sent ice, mud, rocks and fast-moving water surging through a valley in Nepal, wiping out entire settlements in their path. Videos showed people attempting to flee as walls of water and debris swallowed buildings, tore down bridges and power lines, and washed away trees, boulders and vehicles.“It was a horror to walk around. It looks like a bomb blew up, a bomb made of mud, there’s nothing left,” David Fisher, head of the Nepal delegation for the International Federation of Red Cross and Red Crescent Societies, told Bloomberg. “People have lost everything.”Fisher on Saturday visited Nuwakot , an affected district still partially accessible by road. Thousands of people who have been displaced are taking shelter in any surviving buildings on higher ground, including houses of worship, hospitals and government buildings, he said.Nepal has mobilized over 18,500 military and police personnel on challenging rescue missions, including in settlements steeped in sludge and at hydropower projects where workers have been trapped in tunnels. Tunnel experts from India and China have joined in rescue efforts as well.