The U.S. Attorney General is expected to announce a federal investigation into the Baltimore Police Department’s to determine whether the city’s officers have shown a pattern of excessive force. The official announcement could be made as early as Friday, according to reports based on anonymous sources posted by the New York Times, the Associated Press and the Washington Post.

Baltimore Mayor Stephanie Rawlings-Blake has requested a federal investigation of the police department, saying she needs “any and all resources” to repair the “fractured relationship” between the city's residents and officers. Sen. Barbara A. Mikulski (D-Md.) has also expressed support for a federal probe, saying the community has long suffered from a lack of trust in its police force.

The city erupted into riots on April 27 following the funeral of Freddie Gray, a Baltimore resident who died in police custody after suffering a severe spinal injury. On May 1, Baltimore State’s Attorney Marilyn Mosby filed charges against six police officers who took part in Gray’s arrest.   

Earlier this week, Attorney General Loretta Lynch testified in front of a Senate Appropriations subcommittee, saying the role of the Justice Department is not only to prosecute wrongdoing but also to prevent it.

“When there are allegations of wrongdoing made against individual officers and police departments, the Department of Justice has a responsibility to examine the evidence and, if necessary, implement changes,” she said.

Federal investigations into possible civil rights violations are already underway at several police departments around the country including Ferguson, Mo. and Cleveland, Ohio. On Monday, a group of 250 community activists in Boston filed a petition with the Justice Department requesting a similar review. A 2014 report by the American Civil Liberties Union showed that 63 percent of stops and searchers conducted by Boston’s police officers targeted black residents, even though blacks make up less than a fourth of the city’s population.

There are nearly 18,000 law enforcement agencies nationwide and in the past 20 years, the Justice Department has conducted 61 investigations on these agencies, Frontline reports.

On Thursday, San Francisco’s District Attorney George Gascón said that he would expand an ongoing investigation over a few instances of inappropriate behavior by police officers and sheriff’s deputies into a larger review to determine if law enforcement officers had also made illegal arrests based on systemic bias, the New York Times reports.