WASHINGTON — The Justice Department plans to open a wide-ranging investigation into the practices of the Ferguson, Mo., Police Department following the shooting last month of an unarmed black 18-year-old by a white police officer in the St. Louis suburb, a person briefed on the matter said Wednesday night.

The person said the investigation could be announced as early as this afternoon. Missouri officials were notified Wednesday of the probe.

The investigation will look at the practices in the past few years of the police department, including patterns of stops, arrests and use-of-force, as well as the training the officers receive, the person said.

The inquiry 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 local grand jury is also investigating the shooting.

Police have said the shooting followed a scuffle that broke out after Wilson told Brown and a friend to move out of the street and onto a sidewalk.

Police say Wilson was pushed into his squad car and physically assaulted.