OLIVE BRANCH, Ill. -- An earthen levee along the Mississippi River south of Miller City broke Thursday afternoon, flooding farm land and forcing area residents to flee to higher ground.

The levee broke about 1 p.m., with the flood-swollen river pouring through a gap about 100 feet wide. By late afternoon, the levee break had widened to about 300 feet, and the relentless muddy water was flooding the low-lying Miller City and Horseshoe Lake area of Alexander County.

Illinois Department of Transportation (DOT) officials estimated that the swift-moving river could flood 38,800 acres of mostly farm land to a depth of 7 to 14 feet within one and a half to two days.

Illinois Gov. Jim Edgar viewed the levee break by helicopter within hours after it occurred.

"I think what we saw here unfortunately is not going to be unique," Edgar told reporters at the Cairo Airport following his fly-over of the broken levee and the flooding along the Mississippi.

"We may have a lot of levees that will not withstand the rising water," said the governor, who earlier in the day had visited flood-battered Quincy, Ill.

Edgar had been scheduled to fly into Cairo as the last leg of his flood inspection trip before the levee even broke. He arrived at the airport about 3:30 p.m. and met with Kirk Brown, secretary of the Illinois Department of Transportation, who briefed him on the levee break.

Brown said the levee apparently just gave way under the pressure of the swift-moving, swollen river. The water in the river channel was moving at a rate of about 800,000 cubic feet per second at the time of the levee break.

"It was tall enough, but not strong enough," he said of the levee. "There is going to be a lot of damage."

Across the river in the flood-battered village of Commerce, the Illinois levee break resulted in the water level dropping by about two inches, according to Roy Jones of the town board.

Earlier in the day, Edgar asked the federal government to add the Southern Illinois counties of Alexander, Union, Jackson and Randolph counties to the list of those declared disaster areas.

Such a designation would clear the way for federal disaster relief for flood victims, he said.

Thursday afternoon, emergency operations were set up at the Alexander County Highway Department building at Olive Branch, a town about five miles northeast of Miller City.

By late afternoon, hundreds of people, including volunteers, Illinois National Guardsmen, Coast Guard reservists, Alexander County Sheriff's officers, Illinois State Police, and state highway department crews were hard at work trying to cope with the flooding. State police closed off roads to the flooded area, and farmers moved their tractors and other farm equipment to higher ground.

State officials said about 40 guardsmen were being deployed to the area.

Emergency personnel were being fed at the Horseshoe Lake Community Center in Olive Branch.

Area residents braced for a monumental disaster. "It is going to be the worst one (flood) I believe we have ever had," Louis Maze, chairman of the Alexander County Commission, said as he helped coordinate emergency operations.

"We are evacuating Miller City," said Maze, adding that it appears the fast-moving floodwaters could swamp parts of Olive Branch and Illinois Route 3.

Maze estimated that the flooding was forcing most of the approximately 175 residents in the Miller City and surrounding rural area to move out, although some were vowing to stay.

Maze said authorities were advising anyone living in the area south of Horseshoe Lake to move out.

An emergency shelter was being set up at Egyptian High School in Tamms to house flood victims.

"Definitely, Miller City is in trouble," said Maze.

Ironically, about 100 DOT workers had spent the last three days attempting to shore up what authorities felt was a weak point in the levee only 1 miles north of where the levee broke Thursday.

The levee was erected in 1973 by farmers and helped protect the area from the massive flood that year, said Mike McCrite of Olive Branch.

Andy Clarke of Cairo was busy early Thursday evening helping to sandbag his parents' home along the Miller City blacktop.

Clarke said he and his parents planned to wait out the flood in the house, which sits atop a ridge. But he said the road would soon be a river of water.

He said about 800 families in the Horseshoe Lake area could be affected by the flooding.

"It could be pretty much of a tragedy," he said.