NEW YORK — The postal union says a Shreveport, La., postmark is on threatening letters sent to New York City Mayor Michael Bloomberg and his gun-control group in Washington.
Police say preliminary testing showed the letters contained traces of the deadly poison ricin.
The postal union says on its website that it got its information in a postal service briefing.
Police said Wednesday one anonymous letters was opened Friday in New York at the city's mail facility.
The other was opened Sunday in Washington at an office used by the nonprofit started by Bloomberg, Mayors Against Illegal Guns.
Both were addressed to Bloomberg and contained threats referencing the debate on gun laws.