No sarin found in package sent to Facebook that prompted evacuations, officials say

Facebook buildings that were evacuated Monday after equipment at the company's mail-processing facility in Menlo Park, Calif., detected a toxic chemical in a package reopened Tuesday after further testing revealed no threat, according to the company.

The package was delivered about 11 a.m. Monday to one of Facebook's mail rooms at 1195 Hamilton Court. Machines in the mail room detected the chemical sarin – a potentially lethal nerve agent – inside the package, prompting officials to evacuate four buildings and call authorities.

Sarin is a human-made odorless, colorless chemical that has been used in warfare. Exposure can cause convulsions, paralysis and respiratory failure leading to death, according to the Centers for Disease Control and Prevention.

Fire officials and the FBI were called in to investigate the situation. However, further testing revealed that no dangerous chemicals were present in the package.

"Authorities have confirmed test results were negative for any potentially dangerous substance and the buildings have been cleared for repopulation," Facebook director of corporate media relations Anthony Harrison said in a statement to Variety early Tuesday.

Harrison added that the company's "rigorous security and safety procedures worked as intended to limit exposure" and keep employees safe.