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(CNN) -- Sandbag walls were beginning to rise Tuesday across parts of the Midwest against what the National Weather Service warned could be record flooding in the Mississippi and Ohio river valleys over the next week.
Widespread major flooding is expected in parts of southern Missouri, southern Illinois, Indiana, western Kentucky, northern Arkansas and parts of Oklahoma, said Noreen Schwein, deputy for hydrologic services at the National Weather Service's central region headquarters in Kansas City, Missouri.
Already, governors in Missouri, Illinois and Kentucky have declared emergencies, as have local officials in several counties.
National Guard troops are on the job in Missouri and Indiana shoring up levees and stacking sandbags. Indiana also sent 80 prison inmates to the southwestern part of the state, where record flooding was already reported in Gibson County.
Illinois Gov. Pat Quinn sent 125 members of the Guard to Marion to assist the response in the southern part of the state.
Calls for volunteers to help with sandbagging efforts were going out across the region. Clifton Gentry of Jackson, Missouri, was planning to head to the small community of Dutchtown, Missouri, with his church group Tuesday night to help residents there fill and stack sandbags.
"There's a gas station and probably two, three dozen homes that will be under water tomorrow if something doesn't change," Gentry said. "It's basically just the simple fact that we're told to help those in need, and if I was in that kind of situation I would hope someone would help me."
A levee in Poplar Bluff, Missouri, failed on Tuesday, city and county officials said, sending water flooding into a rural but populated area of Butler County, causing the evacuation of more than 6,000 people. People in the area were asked to leave "as soon as possible," Butler County Sheriff's Detective Scott Phelps said.
A levee protecting Bell City, Missouri, also failed, said Dale Moreland, public information officer for the Stoddard County Emergency Management Agency. Bell City schools let out early Tuesday because buses will likely not be able to navigate flooded roads later in the day, Moreland said. Up to 1,200 people south and east of Bell City faced possible evacuation later Tuesday.
The breach was 95 feet wide and 6 to 8 feet deep. About 25 to 30 residences in in the county were affected by the water and a dozen people have been rescued since Monday, according to Moreland.
A levee also failed in nearby Scott County, Moreland said.
Missouri's attorney general turned to a federal court Tuesday to stop a federal plan to blow a levee to ease pressure on the flood-engorged Mississippi River.
James Pogue, chief spokesman in the U.S. Army Corps of Engineers' Memphis office, said the Birds Point-New Madrid Floodway is a "safety valve" in the current crisis affecting several states along the Mississippi and Ohio rivers.
In Paducah, Kentucky, where forecasters are predicting the Ohio River will rise more than it has in at least 61 years, garbage collection was temporarily suspended because every available worker was installing floodgates before the Ohio River rises too high to contain.
"We are putting all our resources on this catastrophe," City Engineer Rick Murphy said.
Crews were also working to build a steel barrier and extend a levee around the city's convention center, which was at risk of being flooded.
The National Weather Service forecast the Ohio River at Paducah to rise to 55 feet by May 3, 16 feet above flood stage and two feet above the high water mark in 1950.
Paducah resident Jennie Bell, a CNN iReporter, said heavy rains and river water are already covering some streets, including the road she normally uses to drive her daughter to school.
"It's getting hard to get around," she said.
In Clark County, Indiana, flooding has forced some people from their homes in the city of Utica and other nearby communities. Some residents have been evacuated. Others are waiting to see what happens, said Phyllis Wilkins, executive director of the Clark County chapter of the American Red Cross.
"There's a lot of U-Haul trailers sitting in driveways ready to go, people sitting on porches watching the waters rise," she said. "Of course, these are people who've lived on the river for a long time so they're used to that routine."
Record or near-record floods are expected from Smithland, Kentucky, to Cairo, Illinois, on the Ohio River and then south to New Madrid, Missouri, downstream from the juncture of the Ohio and Mississippi rivers, Schwein said. If predictions are correct, the flooding could surpass records set in a mighty flood that inundated the region in 1937.
The Weather Service said the Ohio River at Cairo would crest at 61 feet on May 3, 21 feet above flood stage and 18 inches higher than the 1937 mark. The Mississippi River is forecast to top flood stage as far south as Reserve, Louisiana, according to the agency.
The National Weather Service said snow melt from the upper Midwest and rapid runoff from as much as a foot of rain in Mississippi and Ohio river valley states is contributing to the flooding. Three to 5 inches of additional rain expected in the next two days is built into the flooding forecast, Schwein said.
Another bulge of water from melting snow is working its way down the Mississippi River now, Schwein said. The bulge, currently in Iowa, will extend the flooding but is not expected to increase crest levels, she said.
Springdale, Arkansas, received 17 inches of rain between Friday and midmorning Tuesday. Poplar Bluff, Missouri, saw just shy of 13 inches. Arkansas' Fayetteville and Eureka Springs received more than 12 inches. The total for Carbondale, Illinois, was 8.64 inches and Paducah, Kentucky, was at 8.24 inches.
CNN's Phil Gast contributed to this report.