Just after 11am Pacific Standard Time on July 1, Facebook began evacuating offices at its Menlo Park location following the arrival and identification of a package that was deemed suspicious. The package could potentially contain a toxic material that was meant to harm employees of the tech company, and the FBI has since been involved and will be conducting an investigation.
At the moment there is no confirmation as to what the package may contain and whether it poses any real threat to Facebook employees at the offices where it was discovered, however it was initially suspected to contain Sarin gas, a deadly nerve agent, after Sarin was detected in a mail bag by a machine in the mailing room of Facebook's offices.
Facebook says that it routinely tests mail bags and packages for Sarin and other deadly chemicals or dangerous substances, and it was during one of these routine tests that traces of Sarin were found in one of the mail bags. Officials of the Menlo park Fire Department at the scene noted that the detection of Sarin by the machine that completed these tests could have been a false positive. Facebook isn't taking any chances and promptly began evacuating employees from four different buildings before getting the authorities involved.
According to Facebook, a package that was delivered to one of its mail rooms was deemed suspicious at 11am, which led Facebook to start the evacuations. Facebook states that the authorities have not yet identified what the substance in the package is, though it did note that three of the four buildings which were evacuated have now been cleared for use again so the company can resume operations.
Though three of the buildings have been cleared for repopulation it hasn't been confirmed if any employees have actually re-entered the buildings. The mailbag in which traces of Sarin was detected has been quarantined while the local authorities work to figure out what the substance in the suspicious package is and are able to complete the investigation. No time frame has been mentioned on how long the investigation will take and it's currently ongoing.
Facebook has not yet shared any additional information about the potential attack, but has noted it will inform the public once it has more information to share, which likely means once the investigation has come further along and more information is discovered by all of those involved.
Reports about the incident confirm that hazmat teams have requested the FBI's involvement and are apparently on route to the Facebook offices where the package was identified so that they will be able to work in conjunction with local authorities.
Some employees are being monitored as a precautionary measure to ensure their safety, though no symptoms of exposure have currently been detected. There is no information about how many employees are being monitored however, or about how long they will continue to be monitored before being cleared. Facebook mentions that it wants to make sure its employees are safe, noting that "the safety of employees is a top concern."