A threatening letter that disparages black police officers has been found in mailboxes at a Connecticut police department.

Bridgeport officials said Wednesday state police are investigating the letter, which begins and ends with the term "white power."

The letter singles out black officer Clive Higgins, who was acquitted last month of civil rights violation charges in the beating of a suspect in the racially diverse city. A white officer and a Hispanic officer were sentenced to three months in jail.

The unsigned letter says Higgins doesn't belong on the police force. It also says "these black officers belong in the toilet" and warns Higgins to watch his back.

A black police officers' group says other hateful letters have circulated within the department in the past year.