Kelly A. Frank broke out of Montana State Prison in the Deer Lodge Valley with 22-year-old fellow inmate William Willcutt over the weekend, according to officials.
The pair is believed to have escaped in a truck.
Prison warden Mike Mahoney says, "We have intelligence that leads us to believe these guys may be armed."
In 2005, Frank was accused of conspiring to kidnap the talk-show host's then-infant son Harry from the Letterman ranch in Montana.
After the kidnapping charge was dropped, he was sentenced to 10 years imprisonment after pleading guilty to felony theft and misdemeanor obstruction.
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