The possible presence of a deadly poison caused a Facebook facility in California to be evacuated on Monday (local time).
The mailing facility in Menlo Park was evacuated due to the possible presence of sarin, CNN reports. Sarin is extremely toxic and known as a nerve agent.
It's believed two people were exposed to the poison, after something which was sent to the facility returned positive tests.
Menlo Park Fire marshal Jon Johnston told CNN the incident was contained to one building, and five people were evacuated.
According to Live Science, sarin "interferes with signalling within the nervous system".
"The chemical was initially created to be a pesticide that would kill insects.
"People who are exposed to sarin may also experience seizures," Live Science reports.