DES MOINES, Iowa — Thunderstorms battered Iowa with winds as high as 100 mph early Monday, knocking down trees and power lines and blacking out more than 200,000 homes and businesses across much of the state.

No injuries were reported, and there were only a few reports of structural damage, including a roof torn off a small building at the state prison for women in Mitchellville near Des Moines.

The storms didn't produce a lot of rain, but a wind speed of 100 mph was reported at Dawson, a town of about 150 people 30 miles northwest of Des Moines, the National Weather Service said.

About 177,000 customers of MidAmerican Energy lost power from Sioux City on the state's western edge to the Davenport area on the east. Iowa's other large utility company, Alliant Energy, reported 31,000 customers without power.

"It started about midnight in Sioux City. One of the unique things about this storm was that it never really broke up. It just moved across our entire service territory," said Ann Thelen, spokeswoman for MidAmerican Energy.

Thelen said the major problem was "an enormous number" of trees on power lines. It could take three days to restore power to some areas, she said.

Power failures in Des Moines shut down traffic lights, snarling the morning commute. Police posted signs or directed traffic at the busiest intersections.

At the women's prison, part of the roof hit cars in a parking lot, but no one was hurt, said Fred Scaletta, spokesman for the Iowa Department of Corrections. The building houses a voluntary clothing donation center for inmates who are leaving prison, he said.