SIOUX FALLS, S.D. (AP) – Members of an American Indian tribe in western South Dakota are asking federal officials to reopen and reinvestigate approximately 75 deaths on the Pine Ridge Indian Reservation they say were insufficiently investigated and prosecuted.

Oglala Sioux Vice President Tom Poor Bear and Judiciary Committee Chairman James Toby Big Boy have written a letter to U.S. Attorney Brendan Johnson asking that he demand the FBI and Bureau of Indian Affairs reopen what they believe are unsolved murders on the reservation.

The deaths occurred from 1973 to 2011.

The FBI in 2000 released a report detailing the agency’s investigations into the deaths of 57 people on the reservation in the 1970s. But Poor Bear and Big Boy say they are dissatisfied with that report and that more murders have occurred since.