Portland police and Clear Channel Communications unveil Tuesday more than two dozen Portland-area billboards dedicated to unsolved homicide cases.

Each of the 25 billboards will feature four cold cases, for a total of 10 cases advertised across the city.

The police bureau's Cold Case Homicide Unit has a sergeant and four detectives who are assisted by several retired investigators. Funding for the additional investigators comes from a the U.S. Department of Justice and the National Institute for Justice.

The police bureau has nearly 300 unsolved murders dating back to 1969.