The emergency was the latest consequence of storms and torrential rains that have ravaged the Midwest, from Texas through Oklahoma, Kansas, Nebraska, Iowa, Missouri and Illinois.
Authorities urged residents of several small towns in Oklahoma and Kansas to leave their homes as rivers and streams rose.
The Arkansas River town of Webbers Falls, Oklahoma, was one such town. Town officials ordered a mandatory evacuation Wednesday afternoon because of the river's rising level.
But Wednesday evening, a posting on the town's official Facebook page sounded the alarm about the runaway barges for its 600 residents: "Evacuate Webbers Falls immediately. The barges are loose and has the potential to hit the lock and dam 16. If the dam breaks, it will be catastrophic!! Leave now!!"
There was no word by midnight Wednesday where the barges were on the river, but local television stations showing live video of the river and the lock and dam said they had not yet arrived.
For the third consecutive day, dangerous storms prompted numerous tornado warnings and reports of twisters touching down, most in Missouri and Oklahoma.
The National Weather Service said it had received 22 reports of tornadoes by late Wednesday evening, although some of those could be duplicate reporting of the same twister.
One tornado skirted just a few miles north of Joplin, Missouri, on the eighth anniversary of a catastrophic tornado that killed 161 people in the city. The tornado caused some damage in the town of Carl Junction, about 4 miles (6.44 kilometers) north of the Joplin airport.
A 'violent tornado' touched down in Jefferson City, Missouri, causing possible fatalities, heavy damage at 11:43 p.m. on Wednesday. The mayor of the capital city had earlier issued a mandatory evacuation for an area involving a handful of homes. The city's airport also has been evacuated.
The Arkansas River was approaching historic highs, while the already high Missouri and Mississippi Rivers were again rising after a multi-day stretch of storms that produced dozens of tornadoes. Forecasters predicted parts of Oklahoma, Missouri and Kansas could see more severe weather Wednesday night into Thursday.
"The biggest concern is more rain," Oklahoma Gov. Kevin Stitt said during a news conference following an aerial tour with Tulsa Mayor G.W. Bynum and other officials Wednesday morning.
The deluge inundated roadways, closing highways in 22 Oklahoma counties and 17 Kansas counties, along with more than 330 Missouri roads. Amtrak suspended train service Wednesday and Thursday along a route between St. Louis and Kansas City because of congestion and flood-related delays.
The Arkansas River, which was just above 37 feet (11 meters), or 9 feet (2.74 meters) above flood stage, at Muskogee, Oklahoma, was expected to eventually reach 43.5 feet (13.26 meters). Officials encouraged residents in several communities along the river to leave their homes.
But Bynum, Tulsa's mayor, said his city of more than 400,000 people was safe so far.
"The levee system is working the way it's supposed to right now," he said.
Near Crescent, about 34 miles (55 kilometers) north of Oklahoma City, erosion left several homes hanging over the swollen Cimarron River. One unoccupied home rolled into the river Tuesday, and authorities say others could collapse.
More than 9 inches (23 centimeters) of rain has fallen since Sunday in parts of Oklahoma after an already rainy spring.
"Any rainfall we get just continues to saturate the soils that are already saturated. Especially rivers and streams," said Oklahoma State Climatologist Gary McManus.
"There is simply nowhere for this water to go" as it flows downstream from Kansas, according to McManus.
In Kansas, residents in parts of the city of Iola, along the Neosho River, were being urged to evacuate and officials had set up on emergency shelter at a community college, said Corey Schinstock, assistant city administrator. If the river reaches its predicted crest of 27.8 feet (8.47 meters) Thursday, it would be the second-worst flood ever for the town of about 5,400 residents.
Elsewhere, the Mississippi River was at or approaching major flood stage from Iowa through southern Missouri and Illinois. At St. Louis, the Mississippi was expected to crest Monday at nearly 12 feet (3.7 meters) above flood stage. If that holds, the Coast Guard will likely close the river to navigation for the second time this month.
Along the Missouri River, about 50 levees in Missouri could be overtopped by Saturday as high water levels move downstream, according to the Army Corps of Engineers. The river was expected to crest Thursday at 36.1 feet (11 meters) near the town of Glasgow, Missouri, overtopping agricultural levees and inundating some homes, highways and parkland.
Deaths from this week's storms include a 74-year-old woman found early Wednesday morning in Iowa. Officials there say she was killed by a possible tornado that damaged a farmstead in Adair County. Missouri authorities said heavy rain was a contributing factor in the deaths of two people in a traffic accident Tuesday near Springfield.
A fourth weather-related death may have occurred in Oklahoma, where the Highway Patrol said a woman apparently drowned after driving around a barricade Tuesday near Perkins, about 45 miles (72 kilometers) northeast of Oklahoma City. The unidentified woman's body was sent to the state medical examiner's office to confirm the cause of death. Oklahoma Department of Emergency Management spokeswoman Keli Cain said she isn't yet listed as what would be the state's first storm-related death.
Associated Press writers Jill Bleed in Little Rock, Arkansas; Tim Talley in Oklahoma City; Jim Salter in St. Louis; Terry Wallace in Dallas, Heather Hollingsworth in Kansas City, Missouri, and John Hanna in Topeka, Kansas, contributed to this report.
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