Threatening letters sent anonymously to New York Mayor Michael Bloomberg have tested positive for ricin according to initial testing revealed on Wednesday. 
Threatening letters sent anonymously to New York Mayor Michael Bloomberg have tested positive for ricin, according to initial testing disclosed on Wednesday.
The New York Police Department says that two letters, one opened in New York City and another at the Mayors Against Illegal Guns offices in Washington D.C., contained a pink oily substance that appears to contain ricin, according to preliminary tests. Ricin, a toxic substance derived from castor beans, can be fatal if ingested or inhaled in sufficient quantities.
Both letters included threats to Bloomberg, a vocal advocate of gun control, and made reference to the recent gun law debate. (Mayors Against Illegal Guns is an advocacy group led by Bloomberg).
One of the letters was discovered on Friday afternoon in New York while the other was opened in Washington, D.C. on Sunday. Both were postmarked from Shreveport, Louisiana, on May 20, according to NBC News, and will be subject to additional testing to confirm the results.
The NYPD revealed that members of the Emergency Service Unit who handled one of the letters are being examined for minor symptoms related to ricin exposure. The NYPD says symptoms they experienced on Saturday which have since abated, and that the FBI Joint Terrorism Task Force and the NYPD Intelligence Division are investigating the threats.
Letters recently sent to President Barack Obama and Mississippi Republican Senator Roger Wicker tested positive for ricin as well. The FBI arrested a Mississippi man in connection with those letters last month.
Additional reporting by Jonathan Dienst and Richard Esposito.