Thousands of people in northern California have been told to evacuate their homes after the tallest dam in the US was weakened by heavy rainfall.
The California Department of Water Resources said on Sunday that it was releasing as much as 100,000 cubic feet (2,830 cubic metres) of water per second from the main spillway to try to drain the lake.
The emergency spillway of the Oroville Dam could collapse at any moment, officials said. People living in flood risk areas have been ordered to leave immediately.
Water levels in the reservoir have been rising because of heavy rain and snow in California following years of severe drought. It is the first time that Lake Oroville has experienced such an emergency in the dam’s near 50-year history.
In a statement posted on social media, the sheriff for the area around the Lake Oroville Dam in California ordered residents to evacuate, warning them it was not a drill.
On Thursday engineers began releasing water from the dam after noticing large chunks of concrete were missing from a spillway.
Residents of Oroville, a town of 16,000 people 65 miles (105km) north of Sacramento, have been told to head north. Other cities affected should follow orders from their local law enforcement agencies, officials said.