More than 180,000 residents in northern California have been ordered to evacuate their homes over fears that America's tallest dam is about to collapse.

Oroville Dam impounds Lake Oroville, the second largest man-made lake in the state, located in the Sierra Nevada foothills east of the Sacramento Valley. The problem began when a portion of the dam's concrete emergency slipway eroded, opening up a 200-foot-long, 30-foot-deep hole. Now officials fear the erosion could release flood waters downstream into Oroville town, home to 16,000 people, all of whom have been warned to leave their homes immediately. Other areas currently being evacuated include Marysville, Hallwood, Olivehurst, Gridley, Live Oak, Wheatland, Yuba City and Yuba County. The Butte County Sheriff’ Office released the following statement on Facebook: "This is an evacuation order. Immediate evacuation from the low levels of Oroville and areas downstream is ordered. A hazardous situation is developing with the Oroville Dam auxiliary spillway. Operation of the auxiliary spillway has lead to severe erosion that could lead to a failure of the structure. Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville. In response to this developing situation, DWR is increasing water releases to 100,000 cubic feet per second. Immediate evacuation from the low levels of Oroville and areas downstream is ordered. This in [sic] NOT A Drill. This in NOT A Drill. This in NOT A Drill." Evacuees have been ordered to head north towards Chico, where roads are jammed with traffic, hotels are full to capacity and Red Cross stations have been set up to deal with the influx of evacuees. Governor of California Gerry Brown said the circumstances are complex and developing rapidly.

.@JerryBrownGov Issues Emergency Order to Help Response to #OrovilleSpillway https://t.co/RW8XBlLFT6 pic.twitter.com/ULQGjkt1c1

— Gov. Brown Press Ofc (@GovPressOffice) February 13, 2017