HAMBURG, Iowa (AP) — The rising Missouri River ruptured two levees in northwest Missouri on Monday, sending torrents of flood waters over rural farmland toward a small town in Iowa and a resort community in Missouri.

Water rushing from a 50-foot-wide hole in a levee near Hamburg, in far southwest Missouri, is threatening more people. Flood waters are expected by Tuesday to reach a secondary levee protecting the partially evacuated town of about 1,100 people. But if that levee fails, parts of Hamburg could be under as much as 10 feet of standing water, officials said.

The breach near Hamburg, in far southwest Iowa, is threatening more people. The town of about 1,100 residents was already partially evacuated, and water rushing from the 50-foot-wide hole in the levee is expected to reach a secondary levee protecting the town on Tuesday. If that levee fails, parts of town could be under as much as 10 feet of standing water, officials said.

About 45 miles south, the river punched a 225-foot-wide hole through a levee about five miles northwest of Big Lake in Holt County, Mo. The roughly 30 residents who stayed in the resort town after the river started rising were told to leave Monday.

Iowa officials said they would close more than 20 miles of Interstate 29 in southwest Iowa and northwest Missouri by Thursday.

The Army Corps of Engineers has steadily increased the amount of water it is releasing from dams along the Missouri River to account for excess water from heavy spring rains in the Upper Plains and to clear out space for above-average snowmelt coming down from the Rockies. Releases from the Missouri's five lower dams should reach 150,000 cubic feet of water per second Tuesday — more than twice the previous record releases.

The swollen Missouri River has already flooded several areas in Montana, North Dakota and South Dakota, and officials predict the problems will linger through the summer.

National Weather Service hydrologist Dave Pearson described the breach near Hamburg as "pretty substantial" and said "water is flowing through quickly," but it still must cross several miles of rural land to reach the Hamburg area.

Water was shooting Monday into farmland near one of the three spots where the main levee had previously leaked, said Terry Holliman, who owns a Napa Auto Parts store in Hamburg.

"It's impressive," Holliman said. "The force is unbelievable."

It wasn't immediately clear how deep the floodwaters approaching Hamburg were on Monday or whether they would prove too much for the secondary levee built last week to protect the town. Atchison County officials posted video of the breach showing the water spreading out over a large area of farmland after rushing out of the opening.

About 300 Hamburg residents left their homes and businesses last week under an evacuation order issued after the partial breaches in the main levee, located about 5 miles south in rural Atchison County, Mo.

The Army Corps of Engineers has been building up the secondary levee to protect low-lying areas of Hamburg since the partial breaches. Officials had been able to stabilize the initial leaks but had predicted the main levee eventually would fail. And it did Monday.

Corps projections show that if the secondary levee fails, the volume of water released upstream during a levee break could leave 8 to 10 feet of standing water in the southern part of Hamburg. The area includes manufacturing and agricultural businesses. Water could reach the fire station and city hall, but it likely wouldn't reach the northern part of town where most residents live.

In Missouri, Holt County officials said the other levee breach occurred about 5 miles northwest of Big Lake and southwest of Craig. Most of Big Lake's roughly 150 residents left town before Monday and Big Lake State Park was already closed.

The breach is pushing water into agricultural land, though a private levee that farmers built last year is helping slow the advancing flood, Holt County Clerk Kathy Kunkel said. But officials expect the private levee to eventually fail because of the large amount of water.

The record dam releases are expected to bring the Missouri River 5 to 7 feet above flood stage in most of Nebraska and Iowa before continuing into Missouri, where it may rise 10 feet above flood stage in several places and flow over the top of at least 11 rural levees. This summer's Missouri River flooding could rival the record years of 1952 and 1993 in some places.

The river is expected to remain high at least into August because as the record releases from the dams continue.

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Funk contributed to the story from Omaha, Neb., and Maria Fisher contributed from Kansas City, Mo.

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Online:

U.S. Army Corps of Engineers Omaha District: http://www.nwo.usace.army.mil

U.S. Army Corps of Engineers Kansas City District: http://www.nwk.usace.army.mil

National Weather Service river forecast: http://water.weather.gov/ahps2/index.php?wfo=oax

Copyright 2011 The Associated Press.