A second loud boom may have rattled windows in parts of Rockland County yesterday - and its origin remains as mysterious as the explosive noise that blew through southern Westchester County over the weekend.

"It was about 5:15 a.m., and it woke up the whole house," said Nanuet resident Keith Wallenstein. "The house was shaking. It sounded like someone had flown an F-16 over the house."

"If it was thunder, it had to be right on the house," Wallenstein said. "And I know a bunch of people who heard it within 3 to 4 or 5 miles away. So I don't know if it was thunder."

Spokesmen at several Rockland police departments said they were not aware of any reports of loud booms early Monday morning.

An earlier unexplained "boom" shook homes in parts of southern Westchester early Saturday. That noise, and the one that reportedly woke up parts of Rockland yesterday, was unlikely to be an earthquake, weather pattern, falling space debris or a civilian aircraft, officials from local, state and federal agencies said yesterday.

"It's against regulations to be in supersonic speed or subsonic speed that would create the sonic boom," said Jim Peters, a spokesman for the Federal Aviation Administration. "And the only aircraft that are really equipped to make a sonic boom or can possibly make it are military aircraft. And I don't know what military missions, if any, were flown over the Hudson Valley that would've created that noise. You're looking for a needle in a haystack."

Officials at Westchester County Airport and Stewart International Airport said they had no knowledge of aircraft from their facilities causing the disturbance.

Officials at NASA said yesterday that they had no knowledge of the boom nor any explanations for it. They referred calls to the U.S. Air Force Space Command.

Calls to Space Command headquarters in Colorado seeking comment were not returned.

And no U.S. Coast Guard operations in the area could have generated such a loud noise, Petty Officer Barbara Patton said.

Andy Mussoline, a meteorologist with AccuWeather, said thunderstorms in the Rockland County area early yesterday morning could be a possible explanation for the reports.

However, Mussoline said, the weather during the earlier Westchester incidents was clear.

According to Lower Hudson Valley police reports and numerous callers to The Journal News, the earlier loud boom was heard throughout parts of Yonkers, Eastchester, Bronxville, Tuckahoe and Scarsdale at 12:24 a.m. Saturday.

Police in those communities had no new leads yesterday.

Tuckahoe police said officers went out after the reports came in, but found no obvious cause for the window-rattling noise.

Liz Holland, a Mount Kisco resident, told The Journal News over the weekend that she saw a bright yellow object streaking through the sky in a downward arc. Holland said "it wasn't huge, but bigger than a shooting star."

That prompted speculation that the boom might have been caused by a meteor that sailed over the Lower Hudson Valley.

But Mark Taylor, coordinator of the planetarium at the Hudson River Museum in Yonkers, called the likelihood of it "very rare."

"When people say bigger, they usually mean brighter," Taylor said. "It is possible that something in the atmosphere can do that, but it is very rare. But her seeing it moving in a downward arc would be an optical illusion. You would not be able to see that."

There also have been no confirmed reports of seismic activity over the weekend.

Then yesterday, Wallenstein and two other Rockland readers reported hearing a boom there.

On Wednesday, the Santa Cruz Sentinel also reported a similar noise in California's Central Valley - and another one 12 hours earlier in Orange County, Calif.

Both of the incidents remain unsolved, but officials there have discounted supersonic aircraft as the cause of the noise.

Source: The Journal News