CHICAGO (AP) — The U.S. Justice Department plans to release a major report Friday on the Chicago Police Department after a yearlong civil rights investigation that is expected to find a pattern and practice of violations over many years.

Attorney General Loretta Lynch, Chicago Mayor Rahm Emanuel and Chicago Police Superintendent Eddie Johnson are among officials scheduled to attend a news conference Friday morning and publicly release the report, which is expected to be lengthy. Similar reports in other cities have run well over 100 pages.

The federal government launched its investigation of the 12,000-officer force — one of the nation’s largest — in 2015, in the wake of a video being released hat showed the fatal police shooting of 17-year-old Laquan McDonald. The footage, which showed a white officer shooting the black teenager 16 times in October 2014, prompted protests and calls for radical reforms.

An official familiar with the report told The Associated Press that investigators found Chicago police violated constitutional rights over years, but he declined to offer details. The official spoke on condition of anonymity because he wasn’t authorized to speak publicly about the report.

Chicago Mayor Rahm Emanuel has pushed through some reforms since the investigation began, including an overhaul of a police oversight body and issuing body cameras to officers on patrol. But the report is expected to call for additional, more sweeping changes.

During President Barack Obama’s administration, the Justice Department has conducted 25 such investigations of police from Miami to Cleveland and Baltimore to Seattle.