Aerial shots of flooded areas
The Mississippi River has spilled over two more levees in the US Midwest, adding to the flood misery suffered by the region for nearly two weeks.
At least 20 levees have already yielded to the swollen river this week and up to 30 more are still at risk along the river, US Army engineers believe.
Storms and flooding since 6 June have claimed 24 lives, according to the Associated Press (AP) news agency.
In Iowa, the floods have caused damage estimated at more than $1.5bn (£800m).
The latest two levees to succumb are in the St Louis area of Missouri. Farmland was flooded near the hamlet of Meyer and in the Indian Graves levee district.
Officials pointed out that the levees now in danger mainly protect rural, industrial and agricultural areas, and not heavily populated towns.
The AP reported the death toll of 24 and injury toll of 148 based on federal briefing documents.
In the past few days, Iowa has seen its worst flooding since 1993, with about 25,000 people in the city of Cedar Rapids forced from their homes.
As of Wednesday morning, the federal government had provided about 2.5m litres of water, 146 generators, more than 213,000 meals, more than 10m sandbags and 1,200 rolls of plastic sheeting.
President George W Bush earlier promised help to affected areas.
"I fully understand people are upset when they lose their home. A person's home is their most valued possession," he said.
"We want to work with the state and local folks to have a clear strategy to help people."
Mr Bush is expected to visit the region on Thursday to inspect some of the flood damage.