The video was shot by a KCBS helicopter, the station said Tuesday.
"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," Pentagon spokesman Col. Dave Lapan said.
Lapan said that "all indications" are that the Department of Defense was not involved within the mystery object, and that the contrail might have been created by something flown by a private company.
Normally any missile test would require notification so that mariners and pilots could be warned or air space closed, but that may not have been done in this case, Lapan said.
"It does seem implausible, and that's why at this point the operative term is 'unexplained'," he said. "Nobody ... within the Department of Defense that we've reached out to has been able to explain what this contrail is."
Missile tests are common off Southern California. Launches are conducted from vessels and platforms on an ocean range west of Point Mugu.
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 further details.
"We can confirm that there is no threat to our nation, and from all indications this was not a launch by a foreign military," 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 the U.S. from the threat of missiles or hostile aircraft.