So far, all that David Brooks knows about the 30-inch wide thing that crashed through the roof of his neighbor's house near Fredericksburg, Va., the other day is that it was a UFO -- an unidentified frozen object.

"I didn't think that anybody would believe this," said David Brooks yesterday as he recalled how the object came whistling down from the clouds over the Virginia cornfields. "I was standing outside washing my car when I heard a noise.

"It sounded like something traveling at a high rate of speed. When I looked up, it was coming in at an angle over my neighbor's house. It made a whistling noise, then it crashed through their roof."

The neighbors weren't at home so Brooks, believing no one would accept his version of the incident, gathered up a half-dozen pieces of the ice and stored them in his freezer.

But Federal Aviation Administration officials in Washington, 75 miles north of the crash site, said yesterday they would have accepted Brooks' story without even viewing the evidence.

What probably happened, said spokesman Fred Farrar, was that the home was hit by a chunk of frozen water that had leaked from a defective airplane toilet system.

When aircraft toilet tanks leak, the water often freezes on the exterior of a plane at altitudes of 15,000 to 20,000 feet. When the plane descends, the ice breaks off and plummets to the earth, he said.

"It has happened before," Farrar said.

In rural Spotsylvania County, however, there was consternation at the hole -- "as big as a five-gallon bucket" -- that Mr. and Mrs. Lewis Simms said they found in the roof Tuesday.

The ice tore a gaping hole in the roof, went through the dining room ceiling, blew insulation everywhere and melted on the first floor carpeting.

"It was a real mess," said Lewis Simms who spent yesterday mopping up. "When I opened the door, I said, 'What in the world is going on here?'"

The damage could have been more serious said the FAA's Farrar. A chunk the size of the one that hit the Virginia house "certainly could have" killed someone, he said in response to a question.

Farrar said roofs have been damaged across the country from falling frozen wastes.

"We have a particular problem in Denver," said Farrar, explaining that planes must make rapid descents after flying over the Rocky Mountains. The FAA recently began circulating flyers to law enforcement officials there with instructions on what to do if a home is damaged by airplane ice chunks.

As for David Brooks and his frozen samples, Farrar said he did the right thing. "Tell him to hang on to those chunks," the FAA spokesman said. "We may be able to analyze them."

Meanwhile, the Simms are still waiting to hear from the insurance agent who came out to the house yesterday.

Lewis Simms said he doesn't know if his homeowner's policy covers damage from passing aircraft."I sure hope so," he said.