Washington (CNN) The Justice Department is preparing to bring a lawsuit against the Ferguson, Missouri, police department over a pattern of racially discriminatory tactics used by officers, if the police department does not agree to make changes on its own, sources tell CNN.

Attorney General Eric Holder said this week he expects to announce the results of the department's investigation of the shooting death of Michael Brown and a broader probe of the Ferguson Police Department before he leaves office in the coming weeks.

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Brown's shooting death at the hands of Officer Darren Wilson has thrust Ferguson into the center of a nationwide debate over police tactics and race relations. The Justice Department is expected to announce it won't charge Wilson for the shooting, but it's also expected to outline findings that allege a pattern of discriminatory tactics used by the Ferguson police.

If they don't agree to review and revise those tactics, sources say, the Justice Department would sue to force changes in the department.

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