July 1 (UPI) -- Facebook evacuated four of its buildings in Menlo Park, Calif., on Monday after machinery in its mailing facility detected a package containing the nerve agent sarin.
The company reopened three of the buildings after emergency officials deemed them safe. Facebook said no people were exposed to the possible toxin, though officials initially thought two employees may have been exposed.
The San Mateo County Fire battalion chief said the two employees were being evaluated.
Officials were testing the package in question to determine if the substance was, in fact, sarin. An open air test came back negative for the toxin.
The social media company runs all its mail and packages through a machine that automatically detects dangerous substances.