Following a woefully belated response by California authorities' to the dangerous situation unfolding at the Lake Oroville Dam in Northern California over the weekend, an evacuation order forcing some 200,000 people living below the tallest dam in the US remained in place early on Monday after residents were abruptly told to flee when a spillway appeared in danger of collapse.

The Oroville dam is nearly full following winter storms that brought relief to the state after four years of drought. Water levels were less than 7 feet (2 meters) from the top of the dam on Friday. State authorities and engineers on Thursday began releasing water from the dam after noticing that large chunks of concrete were missing from a spillway.

California Governor Jerry Brown asked the Federal Emergency Management Agency on Friday to declare the area a major disaster due to flooding and mudslides brought on by the storms.

As reported last night, authorities issued the evacuation order on Sunday, saying that a crumbling emergency spillway on Lake Oroville Dam in north California could give way and unleash floodwaters onto rural communities along the Feather River. "Immediate evacuation from the low levels of Oroville and areas downstream is ordered," the Butte County sheriff said in a statement posted on social media.

The video below summarizes the situation at the damaged dam.

Aerial video shows strain on California's Oroville Dam's backup spillway hours before thousands ordered to evacuate. https://t.co/47O8hzBZOS pic.twitter.com/FGuRWFpP0u — ABC News (@ABC) February 13, 2017

Sparking panic, the California Department of Water Resources said on Twitter at about 4:30 p.m. PST (0030 GMT Monday) that the spillway next to the dam was "predicted to fail within the next hour" despite local authorities suggesting the situation was under control for much of Saturday and early Sunday.

As further reported on Sunday night, Butte County Sheriff Korey Honea told an earlier news briefing he was told by experts that the hole forming in the spillway could compromise the structure. Rather than risk thousands of lives, the decision was made to order evacuations.

Officials said they feared the damaged spillway could unleash a 30-foot wall of water on Oroville, north of the state capital Sacramento. They said evacuation orders remained in place for some 188,000 people in Oroville, Yuba County, Butte County, Marysville and nearby communities and would be re-evaluated at dawn.

Luckily, several hours later the situation appeared less dire, as the damaged spillway remained standing. The state water resources department said crews using helicopters would drop rocks to fill a huge gouge, and authorities were releasing water to lower the lake's level after weeks of heavy rains in the drought-plagued state. By 10 p.m., state and local officials said the immediate danger had passed with water no longer flowing over the eroded spillway. But they cautioned that the situation remained unpredictable.

"Once you have damage to a structure like that it's catastrophic," acting Water Resources director Bill Croyle told reporters. But he stressed "the integrity of the dam is not impacted" by the damaged spillway. Any further deterioration may depend on further rainfall in the region, which on Saturday prompted the Lake Oroville dam to spill over for the first time in its 48 year history.

Asked about the evacuation order, Croyle said "It was a tough call to make." He added: "It was the right call to make."

The Yuba County Office of Emergency Services urged evacuees to travel only to the east, south or west. "DO NOT TRAVEL NORTH TOWARD OROVILLE," the department warned on Twitter.

Meanwhile, to help those affected by the spillway failure, evacuation centers were set up at a fairgrounds in Chico, California, about 20 miles northwest of Oroville, but major highways leading south out of the area were jammed as residents fled the flood zone and hotels quickly filled up. Javier Santiago, 42, fled with his wife, two children and several friends to the Oroville Dam Visitors Center in a public park above the dam and the danger zone.

With blankets, pillows and a little food, Santiago said: "We’re going to sleep in the car."

The earthfill dam is just upstream and east of Oroville, a city of more than 16,000 people. At 770 feet (230 meters) high, the structure, built between 1962 and 1968, is the tallest U.S. dam, exceeding the Hoover Dam by more than 40 feet (12 meters).

NBC 24 summarizes the latest situation at the dam:

The Lake Oroville Dam Emergency/Auxiliary Spillway structure has suffered "potentially catastrophic damage" as a result of erosion secondary to water flow. This damage "could result in catastrophic failure of the auxiliary spillway."

The California Department of Water Resources (KWR) has increased exhaust water flow from the gated main spillway to 100,000 cfs in order to attempt to decrease Lake Oroville water levels. The water has quit spilling over the auxiliary spillway at this point. Helicopters will be depositing rock filled containers to strengthen the potential failure point.

The Department of Water Resources (DWR) wants people to know that the Oroville Dam itself is sound, and is a separate structure from the auxiliary spillway.

These developments caused the Butte County Sheriff, Kory L. Honea, to order the mandatory evacuation of the City of Oroville south to the Sutter County Line. Residents are advised to evacuate to one of the shelters listed in the shelter section below. Officials say over 188,000 people have been evacuated in Northern California due to the flooding from the spillways of Oroville Dam.

According to Oroville lake levels have receded to the point that auxiliary spillway flows have stopped. DWR hopes to push over a million acre feet of water over the main spillway in the next week, clearing the way for much needed flood storage in the lake. Governor Brown has issued an emergency order to bolster the state’s response to the situation and support subsequent local evacuations.

The State Operations Center at Cal OES headquarters is in full activation now, gathering and providing information and support to communities and state agencies involved in the Lake Oroville and spillway emergency. Authorities in Oroville and surrounding areas in Butte County have advised residents to evacuate due to instability of the Auxiliary Spillway at Lake Oroville. Butte County disabled residents needing assistance evacuating can dial 2-1-1 for assistance. The main number for Butte County Public Information for this situation is (530) 872-5951. Yuba or Sutter County residents can call 1-866-916-3566.

Butte County offices in the Oroville area will be closed Monday due to the evacuations from the spillway incident.

A Flash Flood Warning is in effect due to potential failure of a portion of the auxiliary spillway of Oroville Dam remains in effect until 4:15 P.M. Monday for south central Butte County.

Meanwhile, authorities warn evacuees that if they find hotels/motels that they believe are exhibiting price gouging (raising their rates just for this occasion), they can report this to the state Board of Equalization. The practice is illegal.