The Twin Towers county jail in downtown L.A. was locked down Friday morning after an employee reported seeing someone entering the building who resembled fugitive ex-cop Christopher Jordan Dorner.

Deputies from the Los Angeles County Sheriff's Department, which runs the jail, swooped down on the facility and surrounded the area as authorities worked to determine who actually was inside the sprawling jail.

PHOTOS: Manhunt for ex-LAPD officer

"Out of a preponderance of caution, we have locked down the jails and closed the street," said Steve Whitmore, spokesman for the Sheriff's Department.

He said the person who resembled Dornan could be a contractor or someone else who works in the jail. It was unclear how long it would take for authorities to check the facility.

TIMELINE: Manhunt for ex-LAPD officer

Earlier Friday, rumors were flying that Dorner, 33, a former LAPD officer wanted in connection with three killings, was in Barstow and the San Diego area. Those reports turned out to be untrue, authorities said.

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-- Robert J. Lopez