Another letter containing possible Ricin was intercepted by the White House mail screening service in Washington on Thursday. The letter has been sent on to the FBI for testing and further investigation.

The White House Secret Service says the letter is similar to the two letters earlier sent to New York’s Mayor Michael Bloomberg. Those letters contained Ricin as well according to an announcement by the New York Police Department today.

Of the two letters sent to Bloomberg, one was opened at a New York mail processing facility on Friday, and the other at the Mayors Against Guns office in Washington on Sunday. In both instances, the letters threatened the Mayor and referred to his anti-gun group.

Bloomberg spoke to reporters on Wednesday, saying, “It’s not the first letter that was ever sent to anybody,” the mayor continued, saying, “In terms of why they’ve done it, I don’t know, the letter obviously referred to our anti-gun efforts, but there’s 12,000 people that are going to be killed this year with guns and 19,000 are going to commit suicide with guns and we are not going to walk away from those efforts.”

Bloomberg is the prime organizer for the anti-gun group which now has over 950 mayors from across the country as members.

A spokesman for the police department said officers who had handled a Bloomberg letter have shown signs of slight ricin exposure.

This is the second time this year that President Obama has been targetted with a Ricin letter. He was one of the intended recipients that also targetted a U.S. Senator and a Mississippi judge last month.