The sheriff's office said it's unusual for a missing person search to go on this long in the town.
"We've had missing persons before, but usually we find them the same day or a couple days later," Poweshiek County Sheriff Thomas Kriegel told ABC News on Monday. "We never had one this long that I can recall."
In this close-knit farming community of about 1,500 people, everyone knows everyone, Kriegel said. But the rural area makes the search difficult.
"We're surrounded by farm ground -- corn and soy beans. Right now the corn is probably eight, nine feet tall. The only way you can search it is basically walk down every other row," he said. "It's difficult. Even the planes flying over have a difficulty looking down in the corn rows."
Crews have searched every road, every ditch and every body of water near town, the sheriff said. On Friday authorities also conducted a large ground search of the areas around Brooklyn -- and at least 250 people came out to help.
In addition, a helicopter and a plane flew over the area, he said, and kayakers searched miles along the small rivers on both sides of town.
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