Adams House Dining Hall is now closed after dinner because of the recent vandalism of three of its paintings.

The vandalism occured the week before Thanksgiving holidays, Lieutenant Lawrence J. Murphy of the University Police said Thursday.

"We think it must have happened sometime between 8 p.m. and 6 a.m., after the dining hall was closed," Murphy said.

Most House dining halls are now open to allow students to study during exam period.

The paintings included an 8-foot tall portrait of John Quincy Adams, a portrait of Samuel Dexter and a landscape entitled "Upland Country."

These paintings, on loan from the Fogg Art Museum, have been returned for restoration.

Murphy said the two portraits were vandalized first and then two days later the landscape "was mutilated." There were not witnesses and there are no leads, Murphy added.

Robert J. Kiely, master of Adams House, said Thursday the security around the dining hall has increased. "We're more careful about locking the dining hall when it's not in use," Kiely said.

"It's a real inconvenience. I do most of my studying in my room or in the dining hall but who wants to study with somebody looking over your shoulder?," one student who refused to give his name said yesterday.

As yet no one can estimate the cost of the damage, Louise T. Ambler, curator of the Harvard University Collection, said yesterday. "The Adams portrait is probably the most valuable, but we don't make appraisals too often," she said.

Harvard has insured all of the paintings, Ambler said yesterday.