A researcher says the FBI’s list of unsolved civil rights-era slayings in Mississippi doesn’t include 11 murder cases recently found in archives kept by civil rights organizations and other groups.

Margaret Burnham, a professor at Northeastern University School of Law in Boston, says many of the missing cases were contained in papers from the National Association for the Advancement of Colored People.

Burnham says they were being investigated by then-Mississippi NAACP field secretary Medgar Evers and should be added to the FBI’s list of unsolved slayings.

The FBI pleaded for information last week on 43 unsolved civil rights-era murders, saying time is running out because potential witnesses and suspects are growing old or dying.