LOS ANGELES — U.S. officials said Tuesday they had no clue what could have created a mysterious plume that streaked across the sky off the Southern California coast Monday night, but they said they didn't think there was any threat to the United States.
Speculation immediately arose that some sort of missile may have been fired after Los Angeles TV station KCBS videotaped the spectacular trail from one of its traffic helicopters.
Marine Col. Dave Lapan, a spokesman for the Defense Department, said the Pentagon was talking to the Federal Aviation Administration and other government agencies but that "so far, we've come up empty with any explanation."
The North American Aerospace Defense Command, the joint U.S. -Canadian agency that monitors the skies for possible air attacks, said it was aware of the report but was "unable to provide specific details."
"There is no indication of any threat to our nation," NORAD said in a statement.
The Boeing Co. occasionally launches aircraft from San Nicolas Island, off the California coast, as part of its anti-missile laser testing programs, but Daniel Beck, a spokesman for the company, said Boeing wasn't involved.
NASA and the Defense Missile Agency did not immediately respond to requests for information.
Jonathan McDowell, an astrophysicist at Harvard University who tracks suborbital launches, said that while the contrail appeared similar to those left in missile test launches, the more likely explanation was that it was simply a standard aircraft contrail that was captured on video from an unusual airborne angle.
Other scientists and satellite observers, neanwhile, said the contrail appeared to be moving too slowly to be the result of any sort of missile launch.