TUSCALOOSA, Ala. (AP) — Leaders of several American Indian tribes are asking the University of Alabama to return nearly 6,000 human remains and artifacts from the school’s archaeological park and museum.

Officials with the Oklahoma-based Muscogee Nation say they’ve tried for six years to get the remains back, but bureaucratic red tape has slowed the effort.

That has frustrated tribal leaders, who believe the remains and artifacts at the university’s Moundville Archaeological Park should be reburied. A university spokeswoman says the school has a desire to further collaborate with the request.

A local news outlet reports that the Muscogee Nation and a half-dozen other tribes are seeking the return of the remains and artifacts.