2 Missouri River levees break in Iowa and Mo.

HAMBURG, Iowa - Federal officials say the swollen Missouri River has punched a nearly 300-foot hole into a levee near the southwest Iowa town of Hamburg, and powerful floodwaters are continuing to widen the breach.

It's one of two levees that ruptured along the river Monday morning, sending torrents of water over rural farmland toward Hamburg and the Missouri resort town of Big Lake.

Officials originally estimated that the levee just south of Hamburg had a 50-foot hole, but it had grown to nearly 300 feet by Monday evening.

Floodwaters are expected by Wednesday to reach the top of a secondary levee protecting Hamburg, home to about 1,100 people.

The Army Corps of Engineers says crews are working to add another 3 feet to that levee. If it breaks, parts of Hamburg could be under 10 feet of standing water.

Terry Holliman, who owns an auto parts store in Hamburg, said water was shooting into farmland near one of three spots where the levee had previously leaked.

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

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

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." He said water was "flowing through quickly" but still must cross several miles of rural land to reach the Hamburg area.

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. Local officials posted video of the breach that showed the water spreading over a large area of farmland.

About 300 Hamburg residents left their homes and businesses last week under an evacuation order after partial breaches in the main levee, which is 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.

Some residents in the flood-threatened neighborhoods were hauling the last of their belongings out of nearly empty houses on Monday, including longtime resident Pat Stoop. The last time her home flooded, in 1993, the water barely crept over the floor but it stayed for weeks. When she returned her ceiling fan was covered in 3 inches of mold.

Thanks to the latest flood threats, she's considering a permanent move from the home where she's lived for more than four decades. Stoop said she was "thinking about 40 different things at once ... You start to do something, and then another thing, and before you know it you have 40 balls in the air. And you keep dropping them."

In Missouri, Holt County officials said the second levee breach Monday 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.

That breach also 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. However, officials expect the private levee to eventually fail because of the large amount of water.

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

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.