Undated (AP) _ Intense thunderstorms rolled across southwest and south-central Iowa Sunday, killing two people and injuring two others and spawning several tornadoes that leveled corn crops and knocked out power to hundreds of residents.

A man and a boy were killed by lightning while sitting under a tree at a state park in Council Bluffs, in western Iowa, and the boy's mother and another youth were injured, the womam critically, said Pottawattamie County sheriff's Lt. Jerry Osler.

West and southwest Iowa were particularly hard hit by severe thunderstorms, which spawned tornadoes in the towns of Carson, Henderson, Griswold and Winterset. No injuries were reported in those twisters.

Fifty to 75 homes were damaged in Winterset, and an aircraft hanage there was destroyed, said Madison County sheriff's Deputy Jeff Nicholl.

''There were lots, dozens, of trees down,'' Nicholl said. ''It just tore a lot of them off at the five-foot level, just twisted them off,'' he said.

''Just from my home in Truro to Winterset there appears to be a very wide swath ... trees are down, several power lines are down,'' said Madison County Sheriff Paul Welch said.

''We'll just be checking the crop damage,'' Welch said. ''That will be the major factor. Corn is nothing but a stubble right now.''

About 500 homes were without power in Winterset, while nearby St. Charles and Truro also were without electricity, said Nicholl.

Scattered showers and severe thunderstorms also occurred from west central through southeast Iowa Sunday afternoon, producing more than two inches of rain in Osceola, about 45 miles south of Des Moines.

Pea- to- marble-size hail also was reported with these storms, and golfball-size hail was reported at Guthrie Center, about 40 miles west of Des Moines.

In Clarke County, where pea-size hail covered the ground, strong winds ripped a roof off a barn as well as uprooting several trees.

Osler identified one of those killed at Lake Manawha State Park in Council Bluffs as Bill Lewis, 14, of Omaha, Neb. He did not immediately release the identity of the man killed.

Betty Lewis, 41, and 14-year-old Jeff Newton of Council Bluffs, were injured, said Osler. Newton was listed in fair condition and Ms. Lewis was listed in critical condition later Sunday at a hospital.