NANTUCKET, Mass. (AP) _ The 300-year-old Jethro Coffin House, the oldest house on this island off Cape Cod and a registered national landmark, has been badly damaged by lightning, officials say.

No one was in the house, which is used as a museum, when it was struck by lightning around 5:15 p.m. Thursday, blowing out about half of the roof, most of the house's leaded glass windows, and damaging the chimney, officials said.

''The lightning went down the chimney and blew the whole thing apart,'' said H. Flint Ranney, president of the Nantucket Historical Association. ''It was incredible.''

There was no fire, but Ranney estimated that about 60 percent of the two- story house was destroyed.

Firefighters shored up the house, which Ranney said would be rebuilt using as much of the remaining original wood as possible.