Firefighters check a Facebook mailing facility in California for the possible presence of sarin.
CNN  — 

Initial tests of an item that tested positive for the nerve agent sarin at a Facebook mailing facility in Menlo Park, California, have been inconclusive, authorities said Monday.

Hazardous material teams responded to the facility Monday afternoon after two people were potentially exposed to the man-made nerve agent, according to Menlo Park Fire Marshal Jon Johnston.

The two people who were exposed did not show any symptoms of sarin exposure, he said.

The item, described as a “large general mail bags” with lots of mail inside, went through one of the Menlo Park facility’s mail scanning machines tested positive for sarin, according to Johnston. He said it could be a false positive and other testing is necessary to confirm the result.

Further testing is being done to get more detailed, conclusive information, including a chemical analysis test to see what’s present, Johnston added.

Results from the second entry are expected in about to be in withing a few hours, he said.

The incident is contained to one building, which has been evacuated, Johnston said. Five people were evacuated. The FBI and other agencies were sent to the scene.

Sarin is an extremely volatile nerve agent because of its ability to evaporate from liquid to gas. It is clear, colorless, tasteless and odorless. People are exposed to sarin through skin contact, eye contact, or by breathing it in.

CNN’s Darran Simon and Hollie Silverman contributed to this report.