Four postal warehouses were evacuated on Monday after parcel erroneously tested positive for sarin nerve agent
Facebook’s Silicon Valley headquarters was given the all-clear on Tuesday after authorities determined that an alert for the deadly sarin nerve agent had been a false alarm.
On Monday morning four of the company’s postal warehouses were evacuated and two Facebook staff were examined by paramedics after a parcel tested positive for sarin in routine tests.
But fire and hazardous materials testing teams found no harmful substances, according to the Menlo Park fire service.
A second test on the parcel returned a negative result, but FBI agents and investigators in protective suits continued to sweep the area into the early hours of Tuesday.
Facebook’s own security staff were also involved in the probe.
The alert was triggered by a machine in Facebook’s postal facility that scans all mail and packages for dangerous substances, the Menlo Park Fire District said.
The Fire District said authorities were called in as an ordinary precaution.
A fire district official said previous such alerts had occurred at Facebook’s headquarters and that the most recent incident had also been a false positive.
Civilian hazardous materials testing equipment can be triggered by phosphorous, antifreeze and some pesticides.
“At 11am this morning, a package delivered to one of our mail rooms was deemed suspicious,” Facebook said in a statement on Monday.
“We evacuated four buildings and are conducting a thorough investigation in coordination with local authorities.”
The incident highlights the risk of attacks on Facebook and other high-profile tech companies.
Last year the headquarters of Google’s YouTube, located near Facebook’s campus, were attacked by a woman who was reportedly retaliating for what she considered unfair restrictions on her videos.