Two anonymous letters addressed to New York City Mayor Michael Bloomberg and his gun control group contained material believed to be the potentially deadly poison ricin, and referenced the debate on gun laws, police said on Wednesday.

The letters were opened in New York on Friday at the city's mail facility in Manhattan and in Washington on Sunday at an office used by Mayors Against Illegal Guns, the nonprofit started by Bloomberg, police said on Wednesday.

Chief New York Police spokesman Paul Browne said preliminary testing indicated the presence of ricin in both letters but that more testing would be done. He said the threats contained references to the debate on gun laws.

"In both letters the content was identical," he said, adding that the packages contained "an oily substance" that was a pink or orange. "One letter was addressed to the mayor personally."

The billionaire mayor has emerged as one of the most potent US gun-control advocates, able to press his case with his public position and private money.

The people who initially came into contact with the letters showed no symptoms of exposure to the poison, but three officers who later examined the New York letter experienced minor symptoms that have since abated, police said.

Latest missive

The letters were the latest in a string of toxin-laced missives. In Washington, 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 US senator and a Mississippi judge. A Mississippi man was arrested in that case.

Browne would not comment on what specific threats were made or where the letters were postmarked. He also wouldn't say whether they were handwritten or typed and whether investigators believe they were sent by the same person.

"In terms of why they've done it, I don't know," Bloomberg said at an event Wednesday night.

One of the letters "obviously referred to our anti-gun efforts, but there's 12,000 people that are going to get killed this year with guns and 19,000 that are going to commit suicide with guns, and we're not going to walk away from those efforts," said Bloomberg, adding that he didn't "feel threatened".

Federal officials and the NYPD were investigating. Browne would not say whether the letters were believed to be linked to any other recent ricin cases.

According to the Centers for Disease Control, 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.

AP-Reuters

(China Daily 05/31/2013 page10)