A person of interest is being questioned in connection with threatening letters sent to President Obama, Mayor Bloomberg and his anti-gun group, according to law enforcement officials.

Authorities were questioning the man to see if he had information related to the threatening letters, which were similar in content and bore the same postmark on the envelopes. Two of them, sent to Bloomberg and Mark Glaze, the director of the anti-gun group, have tested positive for poisonous ricin. Officials were testing the letter addressed to Obama to see if it contained ricin as well.

It’s not clear if officials believe the man being questioned sent the letters to Obama, Bloomberg and Glaze.

The Texas man is described as an Army veteran who is a current civilian employee with the Department of Defense. He has connections to Shreveport, La. and to Texas but is not considered a suspect at this time, the sources said.

The threatening letter mailed to President Obama was received Wednesday at an off-site facility, and did not reach the White House, according to the Secret Service.

“This letter has been turned over to the FBI Joint Terrorism Task Force for testing and investigation,” said Brian Leary, a Secret Service spokesman.

(AP)