The Justice Department said it will conduct a full review of police operations after allegations of excessive force and discriminatory policing, particularly directed against minorities.
Assistant U.S. Attorney General Thomas Perez said the Justice Department alerted Seattle Mayor Mike McGinn and the police department of the comprehensive probe Thursday.
"Based upon information gathered during our preliminary review, we believe a formal investigation is warranted to determine whether there has been a pattern or practice of violations of the Constitution or federal law," Perez said in a statement.
"When conducting investigations such as this one, we aim to gather as much information as possible from as many sources as we can. We will examine department leadership and rank and file officers. We will also engage with the community – a critical part of the process of determining whether violations have occurred and how a police department can be improved."
The Seattle Times said the investigation was broadened after the American Civil Liberties Union of Washington and 34 community groups asked the Justice Department to investigate use of force by police officers in several incidents, including last year's fatal police shooting of John T. Williams, a First Nations woodcarver.