The huge mass of hard brown ice that crashed through Roger Bange's roof Friday afternoon, splattering into hundreds of tiny pieces in his son's bedroom, did have "some kind of weird smell to it," Bange recalls.

Sensing something strange had happened, the Centreville resident put on rubber gloves and scooped up some of the frozen bits into a plastic bag, which he placed in a cooler.

But it wasn't until he reached an inspector from the Federal Aviation Administration on the phone that his worst fears were confirmed.

"It's supposedly human waste," Bange said yesterday from his home about two miles south of Dulles International Airport.

"We will be investigating this, of course," FAA spokesman Fred Farrar told a reporter. "We will attempt to determine if, indeed, it did come from an airplane {toilet}, and it appears there's a good likelihood it did."

Bange, 30, said he was home Friday afternoon around 3:20 with his 9-year-old son Bill, who was out sick from school, when they heard a crash. "The whole house shook," Bange said, adding that he raced outside, as did a neighbor who heard the noise.

When Bange saw that some shingles on his roof were "messed up," he dashed inside and up to his son's bedroom.

There was a two-foot-wide hole in the ceiling, insulation strewn around the room and "brown ice all over the place . . . . It got all over everything," he said.

"It was just a big ball of ice . . . . It was pretty weird," said Bill, who was in his father's bedroom at the time, watching television. "It just went splat and shattered into small pieces -- hundreds and hundreds of pieces. My desk got banged up."

The youth said he was glad he was not in his room at the time " 'cause I could've been hurt really bad."

Bange said he saved some of the frozen material because "I didn't know what it was, or who may want it to find out what it was." Yesterday he moved the bag to his outdoor trash barrel, where chilly temperatures were keeping it frozen, he said.

Though such incidents are rare, Farrar said, they have occurred in the past when the drainage valve on the holding tank of a plane's toilet was not properly sealed before takeoff.

"Every once in a while, the valve does not close properly and the fluid leaks out little by little," he said. At high altitudes, below-freezing temperatures keep the fluid fastened to the plane in a frozen glob.

But as the plane descends and the temperature rises, "the piece of ice tends to loosen. Then you get vibrations from the flaps going down, and it sometimes tends to break the ice loose," Farrar said.

The FAA will be checking to see what flights were passing over Bange's home at the time of the incident, but "we haven't been outstandingly successful in the past in pinning it down" on a particular plane, Farrar said.