CEDAR RAPIDS - Days after it rose out of its banks on its way to record flooding in Cedar Rapids, the Cedar River has forced at least 20,000 people from their homes, officials said Saturday.

Officials guess it will be four days before the Cedar River drops enough for workers to even begin pumping out water that has submerged more than 400 blocks, threatened the city's drinking supply and forced the evacuation of a downtown hospital.

"We're estimating at least a couple of weeks before the flood levels get down right around flood stage and below," said Dustin Hinrichs of the Linn County emergency operations center.

The Cedar River crested Friday night at nearly 32 feet, 12 feet higher than the old record set in 1929.

County Supervisor Linda Langston estimated the number forced from their homes at 20,000 and said that figure could rise as officials got a better grasp of how many neighborhoods were flooded. Cedar Rapids has a population of about 120,000.

Residents have moved to shelters and hotels and many have moved in with friends and relatives. Driving in the area has been difficult for days but got even worse late Friday when the state patrol closed Interstate 380, which links Cedar Rapids to Iowa City. Earlier, officials also closed Interstate 80 at Iowa City, blocking a major east-west route through the state.

About 100 miles to the west, Des Moines was dealing with its first major flooding Saturday as water poured out of the Des Moines River and into a small neighborhood north of downtown.

Even as the river slowly recedes, officials in Cedar Rapids worried that the city's supply of fresh drinking water would run out. Only one of the city's half-dozen wells was working, and it was protected by sandbags and pumps powered by generators.

Preliminary damages estimates in Cedar Rapids reached $737 million, and officials foresee a long recovery.

"It's a bit overwhelming ... " said the city's mayor pro-tem, Brian Fagan. "This is an endurance competition. We have to be patient. We have to be cooperative."

In Des Moines, a levee ruptured early Saturday and allowed the Des Moines River to pour into an area near downtown, and a mandatory evacuation was ordered for 270 homes, authorities said. Many residents of the area already had left after a voluntary evacuation request was issued Friday.

Des Moines city crews and National Guard used dump trucks and front-end loaders to build a temporary berm in a bid to stop the water, but by midmorning they had been ordered to abandon the work because officials expected the berm to also fail. That would leave hundreds of homes unprotected from flooding that had already surrounded the city's North High School.

"Things happened really fast," said Toby Hunvemuller of the Army Corps of Engineers. "We tried to figure out how high the level would go. Not enough time. We lost ground. We didn't want to risk life or harm anyone, and the decision was made to stop."

Bill Stowe, Des Moines' public works director, said he expected extensive damage to about 200 homes in the Birdland neighborhood. "There's not anything else we can do," Stowe said.

Elsewhere, Illinois emergency authorities said a levee along the Mississippi River in far western Illinois burst Saturday morning and voluntary evacuations were under way in Keithsburg, a town of about 700 residents.

"The levee broke in two places," Keithsburg Alderman George Askew, 76, said of the town some 35 miles southwest of Moline. "We're getting under water."

Just south of Cedar Rapids, in Iowa City, Gov. Chet Culver warned that more dramatic flooding could be on the way as the Iowa River rises.

"A real wave of water is on the way as we speak," he said.

At least 438 city blocks were under water in Cedar Rapids, hospital patients in wheelchairs and stretchers were evacuated in the middle of the night, and officials said as many as 10,000 townspeople had been driven from their homes in this city of 120,000.

The flooding was blamed for at least two deaths in Iowa.

Since June 6, Iowa has gotten at least 8 inches of rain. That came after a wet spring that left the ground saturated. As of Friday, nine rivers were at or above historic flood levels. More thunderstorms are possible in the Cedar Rapids area over the weekend, but next week is expected to be sunny and dry.

Gov. Chet Culver declared 83 of the state's 99 counties disaster areas, a designation that helps speed aid and opens the way for loans and grants.

The drenching has also severely damaged the corn crop in America's No. 1 corn state and other parts of the Midwest at a time when corn prices are soaring. Dave Miller, a grain farmer and director of research for the Iowa Farm Bureau, estimated that up to 1.3 million acres of corn and 2 million acres of soy beans - about 20 percent of the state's overall grain crop - had been lost to flooding.

"Farmers have already put a lot of resources into a crop that is now underwater," Miller said.

At Cedar Rapids' Prairie High School, where 150 evacuees waited, people could be seen crying in the cafeteria while others watched flood coverage on TVs set up in the gym. Tables were lined with shampoo, toothpaste, contact lens solution and other items, and piles of clothes were separated by size.

At the school, Lisa Armstrong wept as she watched TV news footage of her own rescue. She saw herself climbing into a boat, and watched rescuers trying to coax her dog out of the house. They finally grabbed the animal and pulled it out.

"I didn't think it was going to be as bad as it was, and we should have got out when we were told to leave," she said. "I didn't think or imagine anything like that."

The city's newspaper, The Gazette, continued to cover the story with the help of emergency generators. But the flood was just outside the front door, and the place had no running water. Portable bathrooms were set up outside for the staff.

"We're putting the paper out through heroic, historic effort by the staff companywide," said Steve Buttry, who started as editor of the newspaper on Tuesday - just one day before the disaster struck.

Des Moines fire officials had no immediate estimate of the number of people urged to evacuate there.