A ricin-tainted letter sent to President Obama has been intercepted by the Secret Service.

President Obama in Asbury Park (Tim Larson, Governor's Office)

The Secret Service confirms that the letter has similar markings to those on an envelope  to a letter received by New York Mayor Michael Bloomberg and an office used by Bloomberg's anti-gun group Mayors Against Illegal Guns yesterday.

The letter to Obama was not opened and was taken to a lab for further testing according to ABC News which reports an anti-gun control message was inside the letter and was also similar to yesterday's letters.

The letter was intercepted by a White House mail screening facility and turned over to the FBI's Joint Terrorism Task Force for testing and investigation.

The writer said he has a "constitutional and God-given right and I will exercise that right 'til I die."  The author warned that the government would have to kill him before he would relinquish his weapons, a source told ABC News.

Obama was also sent a ricin-tainted letter in April, the latest in a string of toxin-laced missives. In Washington state, a 37-year-old was charged last week with threatening to kill a federal judge in a letter that contained ricin. About a month earlier, letters containing the substance were addressed to President Barack Obama, a U.S. senator and a Mississippi judge. A Mississippi man was arrested in that case.

Bloomberg's recent letter was sent from  the Shreveport, Louisiana postal center which handles mail from Louisiana, Texas and Arkansas, so the letter might have come from any of those states.

According to the Centers for Disease Control and Prevention, ricin is a poison found naturally in castor beans. Symptoms can include difficulty breathing, vomiting and redness on the skin depending on how the affected person comes into contact with the poison.

The Associated Press contributed to this report