Service did not alert the White House, the Federal Bureau of Investigation (FBI), and other key agencies, including the CDC, of the discovery and positive tests until November 12. In the November 21, 2003 issue of Morbidity and Mortality Weekly Report the CDC recommended that until Fallen Angel was captured, "healthcare providers and public health officials must consider ricin to be a potential public health threat and be vigilant about recognizing illness consistent with ricin exposure". The CDC's November warning mentioned only the first Fallen Angel letter. The discovery of the ricin letter at the White House facility was not disclosed to the public until early February 2004. The public disclosure of the second ricin letter from Fallen Angel coincided with the discovery of ricin in the mail room of a senate office building. February 2004 mail room contamination On February 2, 2004 in a mail room serving Senator Bill Frist in the Dirksen Senate Office Building, a white powdery substance was found on a sorting machine. Tests on February 3 confirmed that the substance was ricin. The positive test results were indicated by six of eight preliminary tests on the substance. The discovery resulted in more than a dozen staffers undergoing decontamination as well as the closure of the Dirksen, Hart, and Russell Senate Office Buildings. The incident was treated as a criminal probe with investigators looking carefully for any connection between the ricin found at Dirksen and the "Fallen Angel" cases. Investigations Fallen Angel The focus of the probe by the FBI, U.S. Postal Inspection Service (USPIS) and the Department of Transportation's Office of Inspector General fell instantly upon the individual calling themself Fallen Angel in the two letters. The FBI was the lead agency in the Fallen Angel investigation. Agents questioned various individuals during their probe, such as one vocal former trucker in Florida. Federal officials, most notably at the U.S. Department of Homeland Security (DHS), remarked that the letters did not have the hallmarks of international terrorism and were more likely produced by a homegrown criminal. On January 4, 2004 the FBI, along with the USPIS and the DOT, offered a $100,000 reward in connection with the October 2003 case from Greenville, South Carolina. In late 2004 the amount of the reward was increased to $120,000. The criminal has not been captured to date. Dirksen Building contamination Immediately following the incident in Frist's office, both the