Attorney General Eric Holder on Thursday announced a Justice Department civil rights investigation into the Ferguson, Mo., police department following the shooting of 18-year-old Michael Brown, saying federal officials would determine whether St. Louis-area officers “engaged in a pattern or practice of violations of the United States Constitution.”

“People consistently expressed concerns stemming from specific alleged incidents from general police and practices and from a lack of diversity on the Ferguson police force,” Holder said. “These anecdotal accounts underscore the history of mistrust of law enforcement in Ferguson that has received a good deal of attention.”

The Justice Department’s civil rights division will explore accusations of racial profiling and excessive force against the police department in the St. Louis suburb. Ferguson protesters say the shooting of Brown was just the latest example of hostility toward minorities by an overwhelmingly white police force.

Critics of the Justice Department action, however, say the Obama administration is playing politics with the issue and should wait until the completion of the criminal investigation before getting involved.