By Patrick Thomas
A group of Facebook Inc. buildings in Menlo Park, Calif., were evacuated Monday after mail that arrived at a company office tested positive for the nerve agent sarin.
The mail center was evacuated around 11 a.m. Pacific Time (2 p.m. Eastern) after employees were alerted that incoming mail undergoing routine processing tested positive for sarin gas, according to the city's fire marshal.
There were no reported injuries and officials are still trying to determine what caused mail to test positive for sarin, the fire marshal said.
Four buildings were evacuated, three of which have since been cleared for employees to re-enter, a Facebook spokesman said in a statement.
"The safety of our employees is our top priority and we will share additional information when it is available," a company spokesman said.
Sarin is a human-made nerve agent that is a clear, colorless, odorless and tasteless liquid and can evaporate and spread into the environment, according to the U.S. Centers for Disease Control and Prevention.
Write to Patrick Thomas at Patrick.Thomas@WSJ.com