Pentagon officials say they cannot explain reports of a missile launch off the coast of California on Monday.
A CBS News helicopter captured what looked like the vapour
trail of a missile rising from the water about 35 miles (56 km)
offshore."Right now all indications are that it was not [defence department] involvement in this launch" Pentagon spokesman Col David Lapan said.
The Pentagon does not consider the missile a threat.
"So far we've come up empty with any explanation," Col Lapan said. "We're doing everything we can to try to figure out if anybody has any knowledge of what this event may have been."
Under normal circumstances, the launch of a US missile would require several different authorisations and notifications, but none are evident.
It is unclear if the suspected missile was launched from land or sea.