A chunk of ice the size of a volleyball smashed through the roof of his home during a thunderstorm, but Duane Cline assumed it was just another car crashing into his house.

Cline said he was reading the paper in his living room about 8:30 p.m. Monday when he heard the noise. He said he at first thought another car had crashed into his Cedar Mill-area house, as happened a few years ago."I thought a bunch of shelves had fallen, that a car had hit them," said Cline, director of maintenance for the city of Lake Oswego.

But when Cline checked the spare bedroom, he found a foot-long hole in the ceiling and plaster, wood and roof material, along with the ice, which apparently broke into about 20 pieces, the largest about the size of a softball. The ice was milky white and smelled faintly of sulfur.

"You can safely say it was related to the thunderstorm, but I don't think it fell out of the sky by itself," National Weather Service meteorologist Ted Buehner said at Portland International Airport. "It had to have some kind of assistance."

Probably, Buehner said, the ice accumulated on the wing of a plane, then fell off. But he checked with the airport's control tower and was told there were no reports of abnormal ice buildup.

Cline said he plans to store the ice in his freezer and might have it tested.