An inmate known as the "spam king" for sending hundreds of thousands of unsolicited e-mails has walked away from a federal prison camp in Colorado.

U.S. Marshals, the FBI and IRS are looking for 35-year-old Edward "Eddie" Davidson, who left a minimum-security facility in Florence on Sunday.

The U.S. Attorney's Office announced his escape on Tuesday.

The office said Davidson was last seen in the Denver suburb of Lakewood, which is about 90 miles north of the prison camp.

Davidson was sentenced in April to 21 months in prison and ordered to pay $714,139 in restitution.

• Click here to visit FOXNews.com's Cybersecurity Center.