For a few hours yesterday an 8-pound chunk of metal that crashed through the roof of a Jersey City warehouse was an unidentified flying object.

Theories abounded - perhaps it was piece of a plane, or maybe debris from the recent collision in space between a U.S. satellite and a defunct Russian satellite.

But Jersey City police solved the case shortly after noon.

The metal chunk - which took 30 minutes to cool after it crashed through the roof of Al Smith Moving at 33 Pacific Ave. at 9:26 a.m. - turned out to be a missing tooth of a gigantic mulching machine located roughly three football fields away at Reliable Wood Products at 1 Caven Point Ave., police spokesman Lt. Edgar Martinez said.

The brick-shaped block, which measured 6 inches by 4 inches by 2 inches and had two hexagonal holes on the top, cut through the roof, splintered a beam and fell about 10 feet from Al Smith, one of two brothers who own the moving and office furniture company.

Forklifting a sofa on a rack at the time, Smith said he heard a loud crash and saw the object crash onto shelving.

"It sounded like a big explosion. And I didn't know what it was, but I see the hole that was in the roof. When I went up on the rack where it landed it was a block of steel," Smith said. "It was an odd thing to happen and I didn't know what to do so I called the police."

Smith added he planned to buy a lottery ticket since it must have been his lucky day.

The tooth came from a trailer-sized grinder that is used to chop wood down to chip-size pieces, said Reliable Wood Products Vice President Eugene Ciarkowski.

Ciarkowski, who said nothing similar has ever happened at his facility before, said the operator did not notice because of the din created by the powerful diesel engine and grinding wood.

"This is a freak event and it is not something you can anticipate," Ciarkowski said.

The machine, he said, has been shut down pending further inspection to make sure it is safe for operations.

"The good news is that no one was injured," said Jersey City Mayor Jerramiah T. Healy. "It did blast through the roof very close to one of the (owners), but it was his lucky day and nothing happened to him."