Rare winter floods have killed at least 20 people and threatened nearly two dozen federal levees in the midwestern U.S. states of Missouri and Illinois, which have been hit by a record amount of torrential rain in recent days.
Missouri Governor Jay Nixon declared a state of emergency and called out the National Guard to assist.
The U.S. Army Corps of Engineers has deemed 19 levees in the St. Louis area highly vulnerable to flooding, which has also caused untreated sewage to flow into waterways in some areas.
In the St. Louis suburb of Valley Park, Mayor Michael Pennise ordered mandatory evacuations for 350 to 400 homes and dozens of businesses in the section of town near the fast-rising Meramec River.
Forecasters expect the Mississippi River to crest Friday at 15.1 meters (49.7 feet), which would match levels from the "Great Flood" of 1993. The Missouri River is expected to crest at 14.5 meters on Saturday, smashing a previous record.
At least 19 federal levees in the St. Louis area are at risk of being overtaken by the floods, which have also caused untreated sewage to flow into waterways in some areas.
National Guard soldiers will help assist first responders in providing security for evacuated areas and help direct traffic away from road closures, according to Nixon.
The U.S. Coast Guard closed a portion of the river near St. Louis to protect the city and placed a round-the-clock watch over the levees. Residents were asked to help fill sandbags and place them along the river banks.
With part of the river shut down to all vessels, the transportation of agricultural products and other goods had to be halted.
More than 40 people were killed as the rare winter storm system swept across the U.S. during the Christmas holiday season. The storms have also caused the delay or cancelation of thousands of flights, stranding travelers during one of the busiest travel times of the year.