Rare winter flooding continued to wreak havoc in the US states of Illinois and Missouri Monday as waterlogged levees strained to hold back frigid river waters that have claimed the lives of 25 people.

Hundreds of homes and businesses have been swallowed by the muddy waters and more could be lost in the coming days, forecasters warned.

"Levees that hold the water in the Illinois River valley are saturated and some of them are failing," Steve Buan, a hydrologist with the National Weather Service, told AFP.

The trouble started over Christmas when a huge storm dumped as much as 10 inches of rain along the Mississippi River valley, which was already saturated from heavy rains earlier in the month.

Missouri's rivers rose faster -- some breaking records by more than four feet (1.2 meters) -- as the water rushed down hills and mountains.

The floodwaters have crested in most areas of the state now, though dozens of roads remain swamped and hundreds of people are still waiting to see what remains of the possessions in their inundated homes.

Much of central and southern Illinois, however, is "pool table flat," Buan said, so the runoff took a lot longer to reach the Illinois River, which is not set to crest until later this week.

"It's extraordinarily unusual," Buan said in a telephone interview.

"We're not expecting to do flood forecasting at Christmas and New Year's. We're looking for how much snow is accumulating, how fast the ice is building."

- Could worsen spring floods -

The upper Mississippi has never been this high in December since settlers first began recording its levels in the 1870s, Buan said.

Communities as far south as Louisiana are bracing themselves as the floodwaters make their way slowly downriver. But since the Mississippi widens as it approaches the Gulf of Mexico, Buan said it should not be as devastating as what Illinois and Missouri are experiencing.

"There's some concern that ... with the spring rains, when they inevitably come, we're going to see a return to flooding because we have such a high river to start with," Buan said.

Officials in Illinois said they are carefully monitoring the stressed levee system in hopes that they will be able to withstand the floods.

"The water will still be fairly high for several days if not weeks to come," said Patti Thompson, a spokeswoman for the Illinois Emergency Management Agency.

"The longer it stays up the more pressure it puts on the levees."

The state has already distributed over a million sandbags to try to shore up the levees and protect homes and businesses in the largely areas impacted by the flooding.

"A lot of what you're seeing is water over farmland or open spaces. But there are homes and communities that have been affected," she told AFP.

"We'll just have to wait for the water to go down to get a better idea of what that impact is."

The bodies of ten people have been recovered from the flood waters in Illinois, Thompson said. A family of five was swept off the road during the storm and the other five died while driving through the floodwaters in recent days.

The bulk of the 15 people killed in Missouri also died while attempting to drive across flooded roads.

The Christmas storm unleashed tornadoes, freezing rain and flooding and dumped deep piles of snow across a huge swath of the United States. It was also blamed for the deaths of 11 people in Texas, 11 in Mississippi and six in Tennessee. Alabama and Arkansas each reported two storm-related deaths while Georgia had one death.