Facebook headquarters cleared after false threat

Police flooded Facebook's headquarters in Northern California to investigate a threat they later found wasn't credible.

Menlo Park police Commander Dave Bertini says Facebook's campus was locked down last night after San Francisco police passed on a report of a threat shortly after 7 pm local time.

Bertini says the threat was found to be unsubstantiated and not credible, and would not give further details. The area was declared safe, and employees were allowed to leave about 8:30 pm.

More than 6,000 people work for the social media giant, but it wasn't clear how many were at the headquarters at that hour.