FILE - In this Nov. 8, 2010 file photo, pedestrians hike one of the trails at Effigy Mounds National Monument in Harpers Ferry, Iowa. A 1990 theft of historically significant Native American remains by a national monument superintendent entrusted with protecting them, was larger and more harmful than previously acknowledged. The case is scheduled to end in a federal courtroom when retired Effigy Mounds National Monument superintendent Thomas Munson is sentenced for carrying out the theft. (Justin Hayworth/The Des Moines Register via AP File)
FILE - In this Nov. 8, 2010 file photo, pedestrians hike one of the trails at Effigy Mounds National Monument in Harpers Ferry, Iowa. A 1990 theft of historically significant Native American remains by a national monument superintendent entrusted with protecting them, was larger and more harmful than previously acknowledged. The case is scheduled to end in a federal courtroom when retired Effigy Mounds National Monument superintendent Thomas Munson is sentenced for carrying out the theft. (Justin Hayworth/The Des Moines Register via AP File)

Iowa City, Iowa — A 1990 theft of historically significant Native American remains by a national monument superintendent entrusted with protecting them was larger and more harmful than previously acknowledged, internal National Park Service documents show.

The case is scheduled to end in a federal courtroom Friday when retired Effigy Mounds National Monument superintendent Thomas Munson is sentenced for carrying out the theft. The 76-year-old has apologized and hopes to avoid a prison sentence. But documents obtained by The Associated Press under the Freedom of Information Act point to wider problems at the federal park along the Mississippi River in northeast Iowa. A series of superintendents were warned that the museum’s entire collection of human bones had gone missing under Munson, but they did little to find them and failed to notify affected tribes. Even the current superintendent called it a “debacle” that would hurt the agency for years.

The bones, which were from more than 40 Native Americans who lived and died in the area between 700 and 2,500 years ago, had been dug up from sacred tribal burial sites during archaeological excavations from the 1950s through the 1970s and were kept in the museum’s collection.

In 1990, Munson was worried about the impact of a new law that would require museums to return the remains of ancestors to their affiliated tribes along with any sacred objects with which they were buried. In July 1990, he ordered subordinate Sharon Greener to pack them up in two boxes and help load them in his car. They sat in his garage in Prairie du Chien, Wis., for the next two decades and suffered damage due to “wildly inappropriate storage conditions,” records show.

The agency fired Greener, who appealed and argued she was being made the scapegoat after trying for years to bring the theft to light. The agency later quietly rescinded her termination and allowed her to retire.

Current Superintendent Jim Nepstad, who finally helped uncover Munson’s theft, wrote in a memo that the case “has, and will continue to cause, profound damage to the credibility and reputation of the National Park Service.”