Emergency workers have removed almost 3 million cubic yards of debris — enough to fill 30 football fields, each 50 feet high — from the states hit by Hurricane Katrina.

The total includes 1.8 million cubic yards of tree limbs, lumber, upturned metals, trash and other bulk left behind in Mississippi; 801,000 cubic yards in Louisiana; and 344,000 cubic yards in Alabama.

But by the time all the debris is cleared, federal and state officials expect the total to reach 80 million cubic yards. The estimated breakdown is 55 million from Louisiana, 23 million from Mississippi and 2 million from Alabama.

That's enough to fill 800 football fields, each 50 feet high. The amount would be 200 times the size of Egypt's Great Pyramid of Giza (search).

Federal emergency officials said Wednesday the debris is overwhelming landfills and impromptu staging areas, and requiring material to be burned nonstop. That includes the contents of thousands of people's homes that were destroyed or ruined.

Cleaning it all up is expected to take almost until the start of next summer.

"With the amount of debris that is on the ground, this is an extreme undertaking, a massive operation," said Kevin Jasper, a project manager for the U.S. Army Corps of Engineers (search) in Mississippi. "This is far and above what Hurricane Andrew did."

Hurricane Andrew, which devastated South Florida in 1992, was one of only three known Category 5 hurricanes to have hit the U.S. mainland. But on Wednesday, Hurricane Rita, threatening Texas, was upgraded to that highest category. Katrina hit the shore last month as a Category 4.

No one knows for sure how much of the debris in each of the states contains hazardous waste, the Environmental Protection Agency and other federal and state agencies agreed Wednesday in a briefing for reporters on the debris in Mississippi.

The Coast Guard said it has identified 350 damaged boats in Mississippi that could pose dangers because they contain oil that is leaking or some sort of hazardous materials.

Hundreds of thousands of cars and some hazardous waste rail cars also are believed to be submerged, mainly in the New Orleans region.

Charles Chisolm, executive director of the Mississippi Department of Environmental Quality (search), said the debris is being taken to the state's existing dumps, which include 17 municipal and 150 commercial landfills and 40 transfer stations. Some closed facilities might have to be reopened.

"We do not have enough disposal space," he said.

Roadways are clogged with debris, forcing hundreds of highway crews to use chain saws and shovels to remove the obstacles. Agriculture officials have removed drowned farm animals.