A federal investigation into the United States' dark history of Native American boarding schools has found "marked or unmarked burial sites" at 53 schools and identified more than 500 student deaths.
Interior Secretary Deb Haaland, the first Native American cabinet member, last year announced the investigation, speaking through tears and in a choked-up voice during a media conference in Washington.
"The federal policies that attempted to wipe out Native identity, language and culture continue to manifest in the pain tribal communities face today," Ms Haaland said.
"We must shed light on the unspoken traumas of the past."
Government researchers found records on 408 schools that received federal funding from 1819 to 1969, and another 89 schools that did not receive money from the government.
About half the schools were run for the government by, or supported by, churches of various denominations. Many children were abused at the schools, and tens of thousands were never heard from again, activists and researchers say.
The report notes that well-documented "rampant physical, sexual and emotional abuse" took place at the schools, and so far the investigation has uncovered the deaths of 500 children while in school custody.
Investigators said they expect to uncover many more deaths.
Ms Haaland said she was beginning a year-long "road to healing" tour to listen to survivors of the boarding school system.
The next goals of the investigation are to estimate the number of kids who attended the schools, find more burial sites and identify how much federal monies went to churches that took part in the school system, among other issues.
She said Congress had provided $US7 million ($AU10 million) to keep the research going this year, which she said was fundamental to helping Native Americans heal.
A former congresswoman from New Mexico, Ms Haaland in 2020 introduced legislation calling for a Truth and Healing Commission into conditions at former Native American boarding schools. That legislation is still pending.
Deborah Parker, head of the National Native American Boarding School Coalition that is assisting the Interior Department in its investigation, said the report just scratched the surface of the trauma.
"Our children had names. Our children had families. Our children have their own languages," she said at the media conference.
"Our children had their own regalia, prayers and religion before Indian boarding schools violently took them away."
