WASHINGTON, D.C. — Trucking has been implicated in an investigation of three letters containing poison addressed to the White House and US DOT.

The deadly poison, called ricin, was included in three typewritten letters signed by “Fallen Angel.” The letters warned more ricin would be used or “dumped” unless the new hours of service regulations which came into effect in the U.S. Jan. 4 are dropped.

“Fallen Angel” claims to be the owner of a tanker truck fleet company. Two letters were discovered Oct. 15 and Nov. 6 respectively. The third, addressed to the White House, was only disclosed by the FBI yesterday.

The trucking industry has been working with the FBI and the U.S. Transportation Department inspector general’s office on the investigation. The American Trucking Associations (ATA) have sent out bulletins urging members to keep a sharp eye out for people “displaying aggressive behaviour” or engaging in suspicious activity.

The ATA has also asked members to “be alert for either a potential disgruntled trucking company, trucking company employee or person purporting to be from the trucking industry” who has made threats in the past against government agencies.

The FBI has also offered a US$100,000 reward for information leading to an arrest in the “Fallen Angel” case.

There is no known antidote for ricin, a strong toxin made from castor beans, but it is considered a less effective weapon for causing mass casualties than anthrax, because it is difficult to make airborne and requires inhalation of large quantities to be fatal.

No one has fallen ill in any of the incidents. In fact, one of the letters was in an envelope on which a typewritten warning was written: “Caution RICIN POISON.”

– With files from Associated Press