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Law enforcement officials tell NBC New York that the FBI and NYPD are aware of threats made on a Jihadist website about wanting to target David Letterman for jokes about the death of Osama bin Laden.
One threat called for an attempt to cut off his tongue.
"We have monitored that site and are aware of the threat and we are investigating it," said Paul Browne, NYPD spokesman.
Officials say they know of no specific plot at this time.
A spokeswoman for Letterman did not immediately comment.