PORTLAND (AP) – Federal officials completing a three-day visit to investigate whether the Portland Police Department systematically violated civil rights say the inquiry is about halfway done.

The review is expected to take six to 12 more months.

Members of the U.S. Department of Justice’s Civil Rights Division returned to the city to meet with officers, ride with patrol teams and interview the city panel that reviews police internal affairs investigations.

The four-member DOJ team also met with city officials to discuss the status of the investigation and to clarify information contained in a letter two months ago that spelled out what investigators viewed as deficiencies in written police policies.

The DOJ told officials Monday that the letter was a collection of best practices, which it recommends but does not at this point require.

If the DOJ finds constitutional violations, it will enter into a memorandum of agreement with the city that includes required changes in police policy and practice.

The police department more than a year ago invited the DOJ to investigate whether a pattern or practice of civil rights violations exist in Portland following a series of excessive force cases against officers. The city decided a review by an outside agency was necessary to identify any deficiencies and restore public confidence in the department.