Ricin-laced letter sent to the White House WASHINGTON - A letter apparently containing ricin, similar to those previously addressed to New York Mayor Michael Bloomberg, was intercepted at a White House mail screening facility, the Secret Service confirmed Thursday. The letter has been turned over to the FBI Joint Terrorism Task Force for testing and investigation, Secret Service spokesman Ed Donovan said. On Wednesday, police revealed that letters threatening Bloomberg because of his stand in favor of gun control had tested positive for ricin. Officials have said the letters addressed to the mayor and to a gun-control organization he has funded, Mayors Against Illegal Guns, were postmarked in Shreveport, La. An unspecified number of New York Police Department personnel reported minor symptoms from the poison that have since abated, NYPD Deputy Commissioner Paul J. Browne said in a statement. "The writer, in letters, threatened Mayor Bloomberg with references to the debate on gun laws," Browne said. Civilian personnel in New York and Washington who came in contact with the opened letters remain asymptomatic. Preliminary tests on both letters came up positive for ricin, a poison that occurs naturally in castor beans and that can be fatal in small doses when inhaled or ingested. Members of the NYPD Emergency Service Unit briefly suffered "minor symptoms" after dealing with the New York letter, which also tested positive for the poison at the National Bioforensic Analysis Center in Maryland on Wednesday, Browne said. Bloomberg, one of the highest-profile figures in the nation backing stricter gun control rules, co-founded Mayors Against Illegal Guns in 2006. The letters marked the second high-profile ricin scare this year. Federal officials last month arrested James Everett Dutschke of Tupelo, Miss., and charged him with manufacturing ricin and mailing letters tainted with the poison to Obama, a U.S. senator and a local judge. Dutschke is also charged with trying to frame a rival who was initially arrested in the case.