Article Posted on : - Nov 10, 2010

WASHINGTON (AFP): The US military has so far been unable to explain an apparent missile vapour trail off the coast of California and is still trying to determine its cause, a Pentagon spokesman has said.

KCBS television caught the long exhaust plume on camera as it arced into the evening sky west of Los Angeles Tuesday night, sparking reports of a missile launch.

Colonel David Lapan, a Pentagon spokesman, said so far none of the military or Department of Defence (DoD) agencies that might have launched a missile "have come up and said they were involved in this."

"So we're still trying to find out what the contrail off the coast of southern California was caused by," he said.

"Right now, all indications are that it was not a DoD activity."

NORAD, the North American Aerospace Defence command that tracks missile launches worldwide, said it was looking into the reports but was unable to provide "specific details."

"We can confirm that there is no indication of any threat to our nation and we will provide more information as it becomes available," the command said in a statement.

ContrailScience.com, a website that debunks conspiracy theories linked to contrails, suggested the sighting was an optical illusion.

It said a contrail streaming horizontally from the exhaust of an approaching aircraft can look like a vertical missile shot if the end of the plume is hidden by the curvature of the earth.

Ordinarily, a missile test would involve closure of air space and notifications to mariners of when to stay clear of the area, but none were known to have been made in this case, Lapan said.

He said it was "implausible" that a military exercise would have been conducted so near Los Angeles's busy international airport.

"That's why at this point the operative term is unexplained," Lapan added.