Thunder roared and tornado warning sirens blared, and all emergency workers in the southeast Missouri town of Poplar Bluff could do Monday was hope the saturated levee holding back the Black River would survive yet another downpour.

Murky water flowed over the levee at more than three dozen spots and crept toward homes in the floodplain. Some had already flooded. If the levee broke — and forecasters said it was in imminent danger of doing so — some 7,000 residents in and around Poplar Bluff would be displaced.

One thousand homes were evacuated earlier in the day. Sandbagging wasn’t an option, Police Chief Danny Whitely said. There were too many trouble spots, and it was too dangerous to put people on the levee. Police went door-to-door encouraging people to get out. Some scurried to collect belongings, others chose to stay. Two men had to be rescued by boat.

“Basically all we can do now is wait, just wait,” Whitely said.

It could be a long week of waiting for the rain to stop in Poplar Bluff and other river towns in the Mississippi and Ohio river valleys. Storms have ripped through parts of middle America for weeks, and they were followed Monday by heavy rain that pelted an area from northeast Texas to Kentucky. At least two people were killed in Arkansas amid heavy rain and tornadoes, authorities said.

One person was killed when floodwaters swept her minivan off a roadway and into the Illinois River in the Fayetteville area, authorities said. Faulkner County spokesman Stephan Hawks says one person died in the central Arkansas town of Vilonia, where a path of damage stretched three miles wide and 15 miles long. It wasn’t yet clear how that person died.

Residents of Vilonia told The Associated Press that storms destroyed much of the town of about 3,800 people about 25 miles north of Little Rock. Authorities had closed off the roadways leading into the town.

“The town’s gone,” said Vilonia resident Sheldon Brock, although he said his house was spared.

The storm system that blew through northeast Texas, Oklahoma and Arkansas on Monday was expected to move into Illinois and Wisconsin today, said Greg Carbin, a meteorologist with the Storm Prediction Center in Norman, Okla. At the same time, a second storm system will start along the same path, meaning several more days of rain. That system will continue east through Thursday, he said.

“I think we’ll see substantial flooding,” Carbin predicted, adding later, “Arkansas to Illinois, that corridor, they’ve already have incredible rainfall and this is going to aggravate the situation.”

The region will get at least 6 inches of rain over the next three days, he said. An area east of Little Rock, Ark., stretching across Memphis and up to eastern Tennessee will be hardest hit with 8 to 9 inches.