WASHINGTON - The Justice Department plans to open an investigation into the practices of the Ferguson Police Department following an officer's shooting last month of an unarmed black man in the Missouri town, CBS News has confirmed.

Local and county authorities in Missouri were notified Wednesday of the investigation, a U.S. official told CBS News. The investigation could be publicly announced as early as Thursday.

The official said the investigation will look at the training and practices, including patterns of stops, arrests and use-of-force of the police department.

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The Justice Department is also entering into a more formal arrangement with St. Louis County to provide technical assistance and guidance with police training, the official said.

The investigation is separate from an ongoing civil rights investigation the Justice Department is conducting into the shooting of 18-year-old Michael Brown by Officer Darren Wilson on Aug. 9. A county grand jury is also investigating the shooting, which set off nearly two weeks of unrest in the St. Louis suburb.

The official spoke on condition of anonymity because the investigation, first reported by The Washington Post, had not yet been announced.

Ferguson Police Chief Tom Jackson did not immediately return a call from The Associated Press seeking comment.

The Obama Justice Department has opened 20 of these civil rights investigations of local police departments over the past five years, CBS News' Bob Orr reported. The cities where investigations were held include Detroit, Washington, D.C., Albuquerque, New Mexico, and Newark, New Jersey.