The U.S. Justice Department notified Ferguson, Mo., police officials Wednesday that the federal government would launch a broad investigation into the policing practices of the city, a person briefed on the matter said.
The probe goes beyond a previously announced investigation into the shooting of an unarmed teenager by a Ferguson police officer last month that sparked weeks of unrest in the St. Louis suburb.
Justice officials were expected to formally announce their intentions as soon as Thursday, said the person who was not authorized to comment publicly.
The inquiry, to be conducted by the Justice Department's Civil Rights Division, will examine years of data to determine whether the department engaged in a so-called pattern and practice of discriminatory policing and the use of excessive force, the source said.
Brown, who was unarmed, was shot at least six times on the afternoon of Aug. 9, and his death touched off two weeks of clashes between police and demonstrators in the small city near St. Louis. The majority of residents of Ferguson are black, and the city's police department is overwhelmingly white.
The launch of the wider Justice inquiry was largely expected following Attorney General Eric Holder's visit to the city last month, when he met with community leaders and was briefed on the separate federal inquiry into the shooting of Brown, an African American, by white officer Darren Wilson.
A St. Louis County grand jury also is reviewing the fatal shooting in which Brown was struck six times in a disputed encounter with Wilson.
The Justice Department has moved aggressively against local police departments in recent years.
Less than a month before the Ferguson shooting, the Civil Rights Division issued a blistering assessment of the Albuquerque Police Department, whose officers used deadly force more than 20 times since 2009.
"We concluded that a majority of these shootings were unconstitutional,'' federal authorities said in a April report.
Contributing: William M. Welch