(CNN) -- The flood damage to Iowa crops could reach $3 billion, according to the state's agriculture secretary.
Three pigs stand stranded on the roof of a building Friday in Oakville, Iowa.
"Right now, we have about 10 percent of our corn that has either been flooded out or not planted and about 20 percent of our [soy]beans," Bill Northey said Friday on "Iowa Press," a public television show.
"We're seeing some beans go back in the ground, and if we were to lose that, if we weren't able to replant, that would be $2.5 billion, $3 billion -- a significant amount of damage," he said.
He added that some of the remaining crops would probably have smaller yields.
Flooding in several Midwestern states has killed two dozen people and injured 148, according to the Federal Emergency Management Agency, and 35,000 to 40,000 people in several states have been displaced. Watch an iReporter's chronicle of the floods »
"I think some of this was absolutely uncontrollable," Northey said. "If you are ready for every potential event that could happen once out of every hundred years or 500 years, you're probably not going to be able to be in business and make it on a normal year. So, some of this is just flat-out unpredictable," he said.
In Iowa, where several rivers jumped their banks about a week ago, water covered city blocks, ruined homes and poured over acres of farmland. This week, residents are returning to homes, and officials are assessing damage as the floodwater moves downstream to add to the Mississippi River's flow.
Despite the acres of flooded farmland in Iowa, "there certainly are folks out there with good crops," Northey said. "There's areas with good crops, and within all areas, there's folks with good crops and poor crops," he said.
Flooding of some of the food processing facilities in Iowa also has a "very significant" impact on Iowa's agriculture, Northey said.
"We're just starting to hear some of those things, just starting to figure out. Those change markets, and in many cases those losses, if they are by flooding, in some cases those are not covered by insurance," he said.
On Thursday, President Bush toured the flood-ravaged state by air.
"Obviously, to the extent that we can help immediately we want to help, and then plan for recovery," the president said at Kirkwood Community College in Cedar Rapids, Iowa.
"You're exhausted; I understand that," he said. "The good news is, the people in Iowa are tough-minded people. You'll come back better," he said.
Iowa Gov. Chet Culver, who toured the area with Bush, said, "we will rebuild this state and this city, and it will be even better and even stronger as a result."