MENLO PARK (CBS SF) – A Facebook spokesperson said there were no dangerous substances found after a hazmat situation involving mail sent to the company’s headquarters in Menlo Park prompted evacuations of several buildings.

“Authorities have confirmed test results were negative for any potentially dangerous substance and the buildings have been cleared for repopulation. Our rigorous security and safety procedures worked as intended to limit exposure and keep our people safe,” a company spokesperson said in an email to KPIX 5.

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Around 11 a.m. Monday morning, the equipment that Facebook uses to screen its mail sounded an alarm. Two of three tests on a large mail bag tested positive for sarin, a clear, colorless nerve agent with no taste or odor that can occur in liquid or vapor form.

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Four buildings were evacuated as a result.

Firefighters and hazardous materials crews outside a Facebook mail sorting facility in Menlo Park, July 1, 2019. (CBS)

The San Mateo County hazmat team was called in, as well as the United States Postal Service and the FBI. Then, the Hayward-based California National Guard’s civil support team was brought in to test the mail.

Hazmat teams cleared out around 1 a.m., nearly 14 hours later after the first emergency crews showed up. All buildings have been cleared for re-entry.

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Officials said the two people who handled the suspicious package are doing well.