Ambulances stood ready on dry land while rescuers in boats searched house-to-house Thursday for people who did not evacuate before flooding hit Missouri Valley.
The focus of the searches were flooded subdivisions south of the Union Pacific rail line that runs along the south edge of town.
Late in the afternoon, the searchers were still finding people holed up in homes surrounded by at least a couple of feet of brown water.
The area of modest homes is known by some locals as just "south of the tracks."
Missouri Valley Fire Chief Caleb Wohlers said more than two dozen people had been rescued.
At one point, a rescuers in a boat steered it slowly up and down the grid of streets, its blue light flashing. It worked its way around the neighborhoods, past half-submerged cars, fences and mailboxes.