The "mystery missile" is a vapor trail that crossed the skies off the Southern California coast and resembled a missile launch.
The Dept. of Defense statement from Col. Dave Lapan, the Acting Deputy Assistant Secretary of Defense, reads:
"While there is nothing at this time that leads the Department of Defense to believe this is a missile launch, the department and other U.S. government agencies with expertise in aviation and space continue to look into the condensation trail (CONTRAIL) seen and reported off the coast of southern California on Monday evening.
"All DoD entities with rocket and missile programs reported no launches, scheduled or inadvertent, during the time period in the area of the reported contrail. NORAD and USNORTHCOM confirmed that it did not monitor any foreign military missile launch off the California coast yesterday and has determined that there was no threat to the US homeland.
"In addition, the FAA ran radar replays from Monday afternoon of a large area west of Los Angeles. Those replays did not reveal any fast-moving, unidentified targets. The FAA also did not receive reports of any unusual sightings from pilots who were flying in the area Monday afternoon.
"If any new information comes to light in the coming days, we will update the press and public."
The Defense Department said Tuesday it did not know what created a vapor trail that crossed the skies off the Southern California coast and resembled a missile launch.
Video posted on the CBS News website shows an object flying through the evening sky Monday that left a large contrail, or vapor trail. The video was shot by a CBS affiliate KCBS' helicopter, the station said Tuesday.
Pentagon officials were stumped by the event. "Nobody within the Department of Defense that we've reached out to has been able to explain what this contrail is, where it came from," Lapan said.
While the vapor cloud captured on video resembled that created by a rocket in flight, military officials said they knew of no launches in the area.
Lapan said that "all indications" were that the Defense Department was not involved with the object.
One expert called it an optical illusion. "It's an airplane that is heading toward the camera and the contrail is illuminated by the setting sun," said John Pike, director of the U.S.-based security analyst group globalsecurity.org.
The North American Aerospace Defense Command, or NORAD, issued a statement jointly with the U.S. Northern Command, or NORTHCOM, saying that the contrail was not the result of a foreign military launching a missile. It provided no details.
"We can confirm that there is no threat to our nation," the statement said. "We will provide more information as it becomes available."
NORTHCOM is the U.S. defense command and NORAD is a U.S.-Canadian organization charged with protecting North America from the threat of missiles or hostile aircraft.
Pike said the object could not have been a rocket because it appeared to alter its course.
"The local station chopped up the video and so it's hard to watch it continuously," Pike said. "But at one place you can see it has changed course; rockets don't do that."
Pike said he did not understand why the military had not recognized the contrail of an aircraft. "The Air Force must ... understand how contrails are formed," he said. "Why they can't get some major out to belabor the obvious, I don't know."