WEST ALTON, Missouri (CNN) -- A levee breach on the Mississippi River forced more evacuations from a small community north of St. Louis on Tuesday, and authorities rushed to shore up another section of levee near a power plant.
A 100- to 150-foot section of levee gave way outside West Alton, Missouri, near the point where the Missouri River joins the Mississippi, St. Charles County's emergency management office reported. Residents of an estimated 43 homes in the area, about 18 miles north of downtown St. Louis, have been told to evacuate.
The levee failed around noon (1 p.m. ET). By evening, authorities were scrambling to bolster about a three-quarter-mile section of levee near Portage des Sioux, about nine miles upstream from West Alton.
The area is home to a nearly 1,000-megawatt coal-burning power plant, and officials were hauling truckloads of stone and heavy earth-moving equipment to the site in an attempt to prevent the levee from failing.
The developments occurred a day after authorities had urged about 300 residents to clear out because of another breach, this time along the Missouri on the other side of West Alton, a town of about 500 surrounded by low-lying farmland. Monday's breach sent emergency teams rushing to get hundreds of people to safety, and many residents didn't need to be told twice to get out.
"I want to be safe rather than sorry," Heather Wendle said. "I don't want to take the chances."
Missourians are helping to fortify the levees by sandbagging. There are no reports of homes under water, though murky water could be seen inching close to front doors, Colene McEntee, a St. Charles County spokeswoman, told CNN.
After weeks of heavy rain in the upper Midwest, the Mississippi is currently running more than 10 feet above flood stage at St. Louis, the Corps of Engineers reported. The Missouri, which joins the Mississippi about 5 miles past West Alton, was nearly 9 feet over its banks on Tuesday.
A few months ago, the Mississippi had been running so low that the Corps feared it would have to close the waterway to barge traffic. In December, the Corps of Engineers had hundreds of tons of rock dug out of the river at Thebes, Illinois, about 125 miles downriver from St. Louis, to make sure barges could pass.
But no closures came until Monday, when the Coast Guard shut down a section of the river at St. Louis -- because the water was too high for safe navigation.
Downriver near Cape Girardeau, the river threatened 13 homes, said Eric McGowen, a Cape Girardeau County emergency management spokesman.
No evacuation orders had been issued, but authorities have had to close several roads around the inland farm communities of Dutchtown and Allenville, he said.
"There are thousands of crops underwater," McGowen said. "It's very early in the season. There have been a lot of crops planted."
Both communities lie along a drainage channel built for flood control in the early 1900s, which runs through the corn and soybean fields in the area to the Mississippi. When the Mississippi rises, water from the river backs up in the waterway, McGowen said.
The Mississippi was more than 10 feet over its 32-foot flood stage at Cape Girardeau and is expected to crest Thursday at 45 feet. But more rain is forecast for Kansas, Missouri, Oklahoma and Arkansas over the next several days.