MONTPELIER, Vt. (AP) - Female prison inmates are to blame for a prank that put the image of a pig in a decal on the doors of some Vermont state police cruisers.

Department of Corrections Commissioner Andy Pallito tells WCAX-TV ( http://bit.ly/xtzXer) female inmates at the prison work center in Windsor are responsible for altering the decal in 2009. But he says figuring out specifically who did it is impossible unless someone confesses.

The pig in the 16-inch decal was first noticed by a state police trooper washing his car Feb. 1.

One of the spots on a cow in the state crest was changed to the shape of a pig, a derogatory term for police.

State police say they believe the pig decal has been added to about 30 cruisers in the past year.

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Information from: WCAX-TV, http://www.wcax.com

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