Residents below the tallest dam in the United States, near Oroville in Northern California, have been ordered to evacuate immediately after authorities said an auxiliary spillway was in danger of imminent collapse.
In a statement posted on social media, the Butte County Sheriff stressed the evacuation order was not a drill.
“Immediate evacuation from the low levels of Oroville and areas downstream is ordered,” the statement said.
It was not clear how many people were affected by the order, but more than 160,000 people live in the evacuation area comprising three counties, according to US census data.
The earth-fill dam is just upstream and to the east of Oroville, a city of more than 16,260 people.
Officials hoped to avoid using Oroville Dam’s emergency spillway, fearing it could cause trees to fall and leave debris cascading into water that rushes through the Feather River, into the Sacramento River and on to San Francisco Bay.
Crews prepared for several days, clearing trees and brush.
Water has already begun running over the emergency spillway, according to California’s Department of Water Resources.