(CNN) -- A compromised levee in Poplar Bluff, Missouri, failed Tuesday, forcing authorities to order more evacuations in the region.

The levee failed in at least four locations along a two-mile stretch along the Black River, City Manager Doug Bagby said.

The failure was expected to send flood waters from the Black River racing into a populated but rural area of Butler County, sparing the city of Poplar Bluff, said the city's deputy police chief, Jeff Rolland.

It was unclear how many people might be affected by the flooding, Butler County Sheriff's Detective Scott Phelps said.

While he said he expected flood waters to rise relatively slowly, it was important for people to evacuate the area "as soon as possible."

The city remained at high risk from the levee failing at another location that prompted the evacuation of about 1,000 people from the southern part of the city, Rolland said. About 259 people are sheltered in the city's Black River Coliseum, he said.

The city has received 15 inches of rain in the last four days, Rolland said -- five of them in just one storm yesterday, he said. At least two more inches of rain was on the way, he said.

"It's just extraordinary," he said.
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    Missouri
    National Weather Service
    Floods

Police performed 59 water rescues Monday alone, he said.

Gov. Jay Nixon deployed the Missouri National Guard to Poplar Bluff and the southeastern corner of the state for what the National Weather Service said could be record flooding.

Nixon ordered National Guard troops to help with efforts to shore up levees near Poplar Bluff and other river communities, among other duties.

"A lot of people are getting very worried that they're going to see higher levels than they've ever seen before," said Aaron Luke, a Nashville resident, who visited family in the Poplar Bluff area over the weekend.

Luke left his car at an aunt's house north of Poplar Bluff when rising waters prevented him from leaving the area.

"I had to grab a rental car to get out and return to Nashville," he said, after using a boat to get across a swollen creek.

Authorities ordered residents most at risk to evacuate immediately. Other residents near the river were asked to closely monitor developments and water levels in their neighborhoods, the police department said.

Daryl Nelson helped evacuate his father and sister from the south end of the city.

"You don't know when it's going to be over and you can get back in," he told CNN affiliate KFVS. "It's better than getting everything ruined."

The weather service said the southeastern portion of the city would be inundated if the levee fails. The levee protects Poplar Bluff from the river, which is now more than five feet over flood stage, according to the weather service.

"We've never seen it like this," Stanley Witmer, who has lived in the area since he was a kid, told KFVS. "It's worse than it's ever been."