The Facebook mailing facility near the company's headquarters at Menlo Park, California, was evacuated on Tuesday over the possible presence of nerve agent sarin, authorities said.
Fire Marshal Jon Johnston said two people were exposed to the banned hazardous gas but showed no symptoms. The incident came to light after a mail item in the facility's mail scanning machine was tested positive for sarin. Johnston said that the item could be a false positive and further testing will be conducted to confirm the event.
Facebook spokesperson Anthony Harrison told The Verge that four buildings were evacuated and a thorough investigation in coordination with local authorities was conducted. "As of now, three buildings have been cleared for repopulation. The safety of our employees is our top priority and we will share additional information when it is available," he added.
It is revealed that the package was delivered around 11 am local time to one of the company's mail rooms. Harrison said that the authorities have not identified the substance found.
The San Francisco office of the Federal Bureau of Investigation (FBI) is reportedly assisting the investigation.
What is sarin gas?
Sarin gas is a colourless, odourless liquid chemical warfare agent that can cause death by disrupting the nervous system and lead to respiratory arrest within 10-15 minutes.
It is considered a weapon of mass destruction due to its lethal potency and properties of transforming the odourless liquid into gas. The Chemical Weapons Convention of 1993 has outlawed the production and stockpiling of sarin gas.