A U.S. Army Corps of Engineers says some levees on the Mississippi River in the St. Louis, Mo. area are "very close to overtopping" as flooding continues.

"The communities have sandbag crews out there. We want to make sure they are safe. That's our number one priority," Dan Busse told CTV Newsnet on Saturday.

People are "tired, but they're fighting," he said.

Many people who reside beside the Mississippi have survived other major floods. They seem to be optimistic that they can hold the levees this time, he said.

"It's a very stressful situation, but they are doing the best job they can," Busse said.

The last major flood in the Mississippi basin occurred in 1993. This year's flood was expected to crest at 11.3 metres at St. Louis on Friday, compared to 15.1 metres in 1993.

However, water levels in some towns in northeastern Missouri and Illinois rose beyond what was predicted.

National Weather Service meteorologist Ben Miller speculated that forecast models  had been unable to account for the amount of water flowing into the Mississippi from the three rivers that saw major flooding in Iowa -- the Cedar, Iowa and Des Moines rivers.

The flood crest in Hannibal, Mo. -- the boyhood home of author Mark Twain, and about 160 kilometres north of St. Louis -- was expected to be about one metre below the 1993 record.

Busse said a key difference between now and 1993 is the condition of the Missouri River.

The Missouri is a major river system in its own right, running from Montana to where it joins the Mississippi just above St. Louis. As in 1993, the Missouri is flooding, but at a much lower level than 15 years ago, he said.

"So we have something similar (to 1993) up in Iowa, but as we get down to St. Louis, a much lower level," he said.

In terms of resources, "we have gotten everything we has asked for," Busse said, adding sandbags have come from as far as California.

About two dozen levees have been breached, but no new breaches were reported as of Friday night.

And there are signs the worst may soon be over. Thundershowers are possible in the St. Louis area, but no heavy rain is forecast.

With files from The Associated Press