Facebook mail site evacuated after possible sarin scare

A Facebook mail facility near company headquarters was evacuated Monday after a routine check found mail possibly containing the nerve agent sarin

"Authorities have not yet identified the substance found," Harrison wrote.

There were no reports of injuries, Menlo Park Fire Marshal Jon Johnston said. Incoming mail undergoing routine processing by machine tested positive for sarin, but it could have been a false positive, Johnston said.

"Right now we don't have anybody that has any symptoms," he said. "We're just doing verification."

The FBI is assisting in the investigation, as is common in incidents such as this one.

A drop of sarin on skin can cause sweating and muscle twitching, and exposure to large doses can result in paralysis and respiratory failure leading to death.

The CDC says people who are mildly exposed usually recover completely.