The latest round of flooding in the Midwest has claimed at least four lives, closed hundreds of roads and forced residents of threatened towns to shore up threatened levees with sandbags. In some communities, waters are rising to historic levels.

The National Weather Service issued flood warnings Friday along a large swath of the Mississippi River, as well as flash flood watches for parts of Missouri, Arkansas, Oklahoma and Texas after recent rounds of heavy rain.

"Do not drive or walk through areas where water covers roadway!" the service warned. "The water may be deeper than it appears. Remember... Turn around, don't drown!"

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In southwest Missouri, authorities are searching for a paddler whose kayak overturned in a flooded creek, one day after finding the body of his friend, 23-year-old Alex Ekern. They were among three men who began paddling Wednesday afternoon on Bull Creek near the small town of Walnut Shade when they were swept over a low-water bridge.

The Missouri State Highway Patrol said one of the kayakers was eventually swept downstream, climbed a steep bank and sought help.

Flooding also claimed the life of a camper who was found Wednesday after he was caught in waters from an overflowed creek near the town of Ava, also in southwest Missouri. And in northern Indiana, a 2-year-old was killed when his mother drove onto a flooded road.

As of Friday afternoon, the Mississippi River was closed to all vessel traffic at St. Louis. The U.S. Coast Guard shut down the river for a five-mile stretch, citing not only the extremely high water but also the swift current.

The river is already more than 8 feet above flood stage at St. Louis and expected to rise another 4 feet by Monday.

Closure of river traffic at one of the largest cities on the Mississippi is a huge blow for commerce since many goods are shipped on barges up and down the river.

A statue of explorers Lewis and Clark is surrounded by floodwater along the St. Louis riverfront, Thursday, May 2, 3019. Jim Salter/AP

The Mississippi isn't the only river bulging out of its banks. Moderate flooding at Missouri River towns like Washington and St. Charles in Missouri was causing headaches like road closures, but few homes were impacted.