New York City Mayor Michael 's  office in New York, and his nonprofit group in Washington D.C. were targets receiving poison letters contained with ricin, the NYPD revealed on Wednesday, as reported by ABC News. Two letters were sent to Bloomberg's offices in D.C. And Manhattan. An undisclosed number of NYPD who were responded to on of the letters "are being examined for minor symptoms of ricin exposure," but the it never reached him directly.

"The writer, in the letters, threatened Mayor Bloomberg, with references to the debate on gun laws," NYPD spokesperson Paul Browne said.

In addition to letters sent to Bloomberg, another one was sent to the director of the Mayors Against Illegal Guns in D.C. Browne said. He indicated that preliminary tests on that letter show it also appeared to contain ricin, though thhe Washington police report of the incident said that no hazmat (hazardous) material was found."

Bloomberg, who has long been a proponent for stricter gun control around the control. The mayor voiced that he was undeterred by the letters.

"No, I do not feel threatened," the mayor said. "This was not the first letter that was sent to anybody. In terms of why they did it - I don't know - the letter referred to our anti-gun efforts. There are 12,000 [people] that are going to be killed this year with guns and 19,000 are going to commit suicide by guns and we are not going to walk away from those efforts."

"I speak for close to 1,000 mayors in the effort against gun violence. This is a scourge against the country and we need to make sure to get this under control," he added. "There are people that do things that might appear irrational - things that are wrong," he said. "But it's a complex world out there. And you just have to deal with that."

Ricin is a toxic poison, which comes from castor beans. It is easy to make with recipe instructions available online, experts say.

Last month, ricin-tainted letters were sent to President Obama, and to government offices, including Mississippi Senator Roger Wicker.

"Instead of the drug of choice, [ricin] has become the weapon of choice of people who might be thinking that," a counter-terrorism official said.