Key PointsA machine at a mailing facility in Menlo Park, California, alerted employees Monday that a package might contain sarin, according to fire officials.No employees have been exposed to the substance, the Menlo Park Fire District said.The defines sarin as a "human-made chemical warfare agent classified as a nerve agent."Facebook runs all of its mail and packages through a machine that can detect dangerous substances, according to the fire district. That machine notified workers that the package in question might contain the substance.Fire officials initially reported that two people...…Key PointsA machine at a mailing facility in Menlo Park, California, alerted employees Monday that a package might contain sarin, according to fire officials.No employees have been exposed to the substance, the Menlo Park Fire District said.The defines sarin as a "human-made chemical warfare agent classified as a nerve agent."Facebook runs all of its mail and packages through a machine that can detect dangerous substances, according to the fire district. That machine notified workers that the package in question might contain the substance.Fire officials initially reported that two people...WW…