RICHLAND, Iowa (AP) _ A house exploded during a party Monday afternoon, killing at least seven people and leaving ``just a hole in the ground,'' the sheriff said.

Six other people were taken to hospitals in Iowa City, and three were in critical condition.

The blast destroyed the ranch-style home and destroyed cars parked out front. Hours after the explosion, light smoke was still coming from the charred debris.

``There's just a hole in the ground,'' Keokuk County Sheriff Ron George said. ``When I got here, the house was gone.''

George said the dead were found in the basement.

The cause of the explosion was unknown. George said a propane tank behind the house was still intact.

Maria Reif, who lives two blocks away, said she heard the explosion.

``I was sitting on my front steps and I heard a boom and I saw fire shoot up,'' she said.

Richland is 35 miles southwest of Iowa City.