Letters threatening New York Mayor Michael R. Bloomberg over gun control laws have tested positive for the poison ricin, police said Wednesday.
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 anonymous letters were opened at the city’s mail facility on Gold Street in Manhattan on Friday and by the director of Bloomberg's gun control consortium, Mayors Against Illegal Guns, in Washington on Sunday, police said.
"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.
The FBI will handle the investigation, 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.
He put out a harsh statement last month criticizing lawmakers in Washington who failed to vote for comprehensive background checks and other gun control measures advocated by President Obama after the Newtown, Conn., massacre of 20 first-graders and six educators.
In March, he launched a $12-million ad campaign -- some of it paid for out of his vast personal fortune -- to champion gun control legislation.
The letters to Bloomberg 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.
Pearce reported from Los Angeles and Susman from West Virginia.