Following up on our story from last night about the ricin-laced letters sent to New York Mayor Michael Bloomberg, a similar threatening letter has been intercepted on its way to President Obama: Third Letter Sent to President Obama, Similar to NY Mayor Ricin Letters: Officials.

The letter, first reported by NBC 4 New York, is being tested for ricin. It was received Wednesday at an off-site facility, and did not reach the White House, according to the Secret Service. …

The text of that mailing was identical to the letters sent to the mayor and his gun group, which threatened: “what’s in this letter is nothing compared to what I’ve got planned for you,” police and law enforcement sources said.

One letter was discovered at City Hall’s mail sorting facility at 100 Gold St. on Friday, a law enforcement source told NBC 4 New York. It appeared to contain a pink, oily substance when a mail worker came across it and was immediately flagged as suspicious.

An initial field test didn’t bring up any sign of ricin, a source said. But more preliminary testing Wednesday showed the letter tested positive for ricin. An identical letter containing ricin was sent to the Mayors Against Illegal Guns headquarters in Washington, D.C. and was opened on Monday, police said. …

According to law enforcement sources, the three similar threatening letters were postmarked May 20 in Shreveport, La. and sent without a return address or signature. Sources said the NYPD tried to pull fingerprints off the letter discovered at the city’s mail sorting site, but nothing usable was found. Authorities also plan to check for any possible DNA.

It wasn’t known if any viable forensic evidence was discovered on the letters sent to Washington or the White House. All three mailings read in part: “You will have to kill me and my family before you get my guns. Anyone wants to come to my house will get shot in the face. The right to bear arms is my constitutional God given right and I will exercise that right till the day I die.”