Topeka ? Rising waters along the Missouri River are forcing Kansas officials to close a portion of a state highway in northeast Kansas as communities began to voluntarily evacuate their homes.

The Kansas Division of Emergency Management said Tuesday that Kansas 7 north of Sparks in Doniphan County to the Nebraska border was closed. High water over the roadway was expected to keep the highway closed for several days.

Missouri Gov. Jay Nixon on Tuesday sent a request to President Barack Obama to declare a federal emergency because of the flooding, which has seen several communities in Andrew, Atchison, Buchanan, Hold and Platte counties evacuate residents. The water has forced the closing of portions of Interstate 29 and U.S. 136 and 159.

“A federal emergency declaration is another important step in our work to bring every resource to bear to fight these historic floods that are impacting so much of Missouri,” Nixon said in a statement.

Kansas Gov. Sam Brownback made a similar request on Friday for Atchison, Doniphan, Leavenworth and Wyandotte counties.

The Missouri River has been rising for weeks because of heavy rains and snow melt along the river’s headwaters, forcing the U.S. Army Corps of Engineers to open flood gates and sending water downstream at 160,000 cubic feet per second.

On Monday, residents of Elwood and Wathena in Doniphan County began leaving their homes in potential flood areas. Kansas officials were urging residents to heed the warning and get to higher ground for their own safety. The Kansas Highway Patrol began assisting Elwood police on Tuesday with law enforcement in the city.

“Flood waters can be deceptive. It only takes 18 inches of water to float a car,” said Angee Morgan, deputy director of KDEM.

The Kansas National Guard has placed approximately 200 soldiers on standby to assist with Doniphan County evacuations and security if the Missouri River reaches 28 feet and continues to rise. Ten soldiers and two vehicles have been patrolling levees in Doniphan County since early June.

Also on Monday, the Missouri Department of Transportation closed a bridge over the Missouri River leading to Atchison, Kan. A small segment of highway near Winthrop, Mo., was closed around 9:30 p.m. Monday.

Road blocks have been set up to notify drivers several miles away that they can’t get across the Amelia Earhart Memorial Bridge leading into Atchison. The only other river crossings open are the U.S. 36 bridge in St. Joseph, Mo., and the Centennial Bridge/Kansas 92 crossing in Leavenworth.

A significant breach of an agricultural levee north of U.S. 59 Monday afternoon caused water to rush into farmland and onto the highway.

Kansas and Missouri transportation agencies have posted updates on road conditions and closures on their websites ahead of the July 4 holiday weekend to alert motorists.