POPLAR BLUFF, Mo. (AP) -- A levee keeping a swollen river from inundating a southeast Missouri town cracked in at least one place Tuesday, but water pouring through the breech was unlikely to force the further mass-evacuation of homes in the area, authorities said.

Crews were also looking into reports of another breach in the levee protecting Poplar Bluff and the surrounding area along the Black River from major flooding, police officer Daron House told The Associated Press. He said officials were planning to evacuate more homes, but that he didn't know how many.

The breach happened southeast of Poplar Bluff in an area that's not heavily populated, Butler County Sheriff Mark Dobbs said Tuesday. The water was pouring into a drainage ditch along a road, and even it if topped the ditch, was unlikely to cause enough backflow to threaten Poplar Bluff homes upstream, he said.

The levee is holding back a river swollen by a powerful storms moving through the Midwest that dumped several inches of rain on the Mississippi and Ohio river valleys over the past week. The storms spawned at least one tornado in Arkansas Monday night that killed four people and carved a wide swath of destruction through the town of Vilonia.

Poplar Bluff deputy police chief Jeff Rolland said Tuesday that more than 6 inches of rain fell on the town on Monday, bringing the four-day total in the area to 15 inches and causing the Black River to pour over the levee in 30 places from Poplar Bluff to the downriver town of Qulan.

More showers and thunderstorms were expected in the area on Tuesday, giving crews that worked overnight to sure-up the levee no rest.

Rolland said street department workers hurriedly filled small boats with sandbags overnight and were able to sure up a vulnerable section of the levee in Poplar Bluff, a town of 17,000 residents that is 130 miles south of St. Louis.

Crews rescued 59 people in 1 1/2 hours late Monday after water spilled over the dam.

A full-scale levee breach could force the evacuation of some 6,000 homes from Poplar Bluff to Qulin and destroy or severely damage 500 homes in Poplar Bluff and its outskirts, Rolland said. Already, 23 small businesses in the area's flood plain have taken on water, he said.

The hotels in town filled up quickly, and 300 people took shelter at the Black River Coliseum, the town's 500-seat concert venue, Rolland said. No deaths or serious injuries have been reported.

Families forced to flee their homes Monday watched as murky floodwater began creeping into their yards and homes. If the levee were to give way, many of those homes would be left uninhabitable. Sandbagging wasn't an option - the river, spurred on by 10 inches or more of rain since last week, simply rose too quickly.

"By the time we realized what was happening it was too dangerous to sandbag," Butler County Presiding Commissioner Ed Strenfel said.

Severe storms that began early last week have hammered the nation's midsection without letup. Again Monday, powerful storms ravaged Missouri, Arkansas, Kentucky, Texas, Tennessee and other states. Authorities said at least seven people were killed in Arkansas - three of them when floodwaters swept two vehicles off of roadways and four when a likely twister tore through Vilonia.

The storm system was expected to move into Illinois and Wisconsin on Tuesday, said Greg Carbin, a meteorologist with the Storm Prediction Center in Norman, Okla. At the same time, a second storm system was expected to start along the same path, bringing several more days of rain, he said.

Governors in Arkansas and Kentucky declared states of emergency. In Kentucky, record flooding is expected over the next few days, partly because of a double-whammy - both the Ohio and Mississippi rivers significantly above flood stage. Several dozen residents were evacuated from the area of Cairo, Ill., where the rivers converge.

The U.S. Army Corps of Engineers was considering the extraordinary step of intentionally breaching the Birds Point levee in southeast Missouri, just downriver of the confluence, in a bid to reduce the amount of water moving down the Mississippi. The move would soak 130,000 acres of farmland, and Missouri Gov. Jay Nixon objected to the idea. A decision was expected Tuesday.

A dam in St. Francois County was in jeopardy of bursting, with a few dozen homes potentially in harm's way. Levees were stressed along the Mississippi River in Pike and Lincoln counties, north of St. Louis.

But by far the biggest concern was Poplar Bluff. The Missouri National Guard sent 200 guardsmen and rescue equipment to the area. Several people had to be rescued by boat, including some who don't live in the flood plain, as heavy rain flooded several streets Monday night.

Police officers spent Monday going door-to-door in the southwest part of town, telling residents to get out. Not everyone did.

Along one road near the levee, children played knee-deep in water. Adults gathered on the porches, seemingly enjoying nature's show.

"I'm not worried. This is my favorite time of the year," 20-year-old Brandon Andrews said, pledging to ride out the flood in his trailer home, even as water lapped against its sides. He didn't have a boat and the water was already too high to drive through, but Andrews said he had been to the store and stocked up on hot dogs, chili and necessities.

Police Chief Danny Whiteley was hoping the water would recede soon enough that flooding would mostly be limited to basements. He wasn't optimistic.

"I guess you'd call it a perfect storm: It's just all come together at once," Whiteley said.

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Pinky Mehta reported from Louisville, Ky., Kristi Eaton and Ken Miller in Oklahoma City, Jeannie Nuss in Little Rock, Nomaan Merchant in Vilonia, Ark., and Hasan Dudar in Indianapolis contributed to this report.