An envelope sent to a South Carolina postal facility contained a vial of ricin and a warning that large amounts of the poison would be dumped into drinking reservoirs if the government did not change a rule requiring truckers to rest after 10 hours on the road, a senior law enforcement official told the Associated Press.

The vial was found at the postal facility in Greenville on Oct. 15, AP said.

American Trucking Associations said in a statement Oct. 23 that the Trucking Information Sharing and Analysis Center had been working confidentially with the Department of Homeland Security to assist the FBI in this investigation.

Although the new hours-of-service rule extends daily driving time by one hour to 11, it also cuts the overall workday an hour to 14 from 15. The approved rule is scheduled to take effect Jan. 4.

Ricin is derived from the castor bean plant and is relatively easy to make, but can be deadly in very small doses, AP said. When inhaled or ingested, fever, cough, shortness of breath, chest tightness, and low blood pressure can occur within eight hours. Death can come between 36 and 72 hours after exposure.

The ISAC is asking the trucking industry to be alert for individuals displaying aggressive behavior or who may be engaged in suspicious activities.

Originally posted on Fleet Financials