The death toll from devastating floods in eastern Libya surged past 11,300 people in the city of Derna alone, overshadowing hopes of finding the thousands of others missing after a rare hurricane-like storm slammed into the North African nation last week.

As rescuers including Libyan fighters and foreign teams combed through the rubble, concerns mounted about the potential health impact, including from cholera, from the contaminated waters. Authorities ordered an investigation into what caused the collapse of two dams that overwhelmed the city.

The United Nations estimated 10,100 people remained unaccounted for, a figure that when combined with fatalities represents about 24% of Derna’s previous population.

“I left Derna today with a heavy heart, after witnessing the devastation caused by floods on lives and properties,” Abdoulaye Bathily, the top UN envoy to Libya, said on X, the platform formerly known as Twitter. “This crisis is beyond Libya’s capacity to manage, it goes beyond politics and borders.”

The catastrophe struck a country already roiled by years of war starting with the 2011 revolt that ousted dictator Moammar Qaddafi. Rival governments in the east and west say they’re working together to provide assistance, while more than a dozen nations are offering aid, including rescue teams and money.