The investigation into the appearance of the deadly poison ricin on Capitol Hill is focusing on a mysterious “Fallen Angel” who threatens to use ricin as a weapon unless new trucking regulations are rolled back, according to the Associated Press on February 5. Federal law enforcement officials said the FBI and Capitol Police Department were investigating the possibility that the same person or persons who made those earlier threats sent ricin-laced mail to Senate Majority Leader Bill Frist, R-Tenn. The typewritten letters, addressed to the White House and Transportation Department and signed by “Fallen Angel,” warned that more ricin would be used unless some trucking regulations that went into effect Jan. 4 were scrapped. Capitol Police Chief Terrance Gainer said investigators have found “no obvious direct connection” between the Frist case and the letters signed by “Fallen Angel.” Those letters were discovered in mail facilities that serve the Greenville-Spartanburg International Airport in South Carolina and the White House. They were found Oct. 15 and Nov. 6, respectively, but the existence of the White House letter was not disclosed by the Bush administration until Feb. 2. The letters, described as nearly identical, claimed that the author owned a tanker truck fleet company and demanded that rules governing the numbers of hours truckers can drive remain unchanged, according to the FBI. The FBI said the South Carolina letter was in an envelope with a typewritten warning “Caution RICIN POISON.” The letter included claims that the author could make much more ricin and would “start dumping” if the new regulations weren't abolished. There was no delivery address and no postmark. The trucking industry has been working with the FBI and Transportation Department inspector general's office on the investigation. The American Trucking Association has sent bulletins to its members urging them to be aware of people ``displaying aggressive behavior'' or engaging in suspicious activity. The FBI has offered a $100,000 reward for information leading to an arrest in the ``Fallen Angel'' case.