They issued an update, just over an hour ago, that the building had been given the all clear.
A spokeswoman said: "We take the safety and security of our people at Facebook extremely seriously and are glad that everyone is safe". They told the public to avoid the area around the 200 block of Jefferson Drive in Menlo Park as officers investigate a bomb threat.
The San Mateo bomb unit responded to the Tuesday afternoon threat at the company's campus in Menlo Park, California, the Menlo Park Police Department said in a statement.
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Menlo Park police confirmed to KPIX that the bomb threat was initially called in to the New York Police Department and the information was relayed to local law enforcement.
Facebook employees have been evacuated from part of the company's sprawling headquarters campus due to a bomb threat.
"Police are investigating a bomb threat". We'll update the story if there are further developments.