[Religion News Service] The United States operated 408 boarding schools for Indigenous children across 37 states or then-territories between 1819 and 1969 — half of them likely supported by religious institutions, according to the first volume of an investigative report into the country’s Indian boarding school system.

“Our initial investigation results show that approximately 50% of federal Indian boarding schools may have received support or involvement from religious institutions or organizations, including funding, infrastructure and personnel,” Assistant Secretary for Indian Affairs Bryan Newland said during a news conference May 11, revealing the results of the U.S. Department of the Interior’s Federal Indian Boarding School Initiative.

The report revealed nearly 40 more schools than the National Native American Boarding School Healing Coalition previously had identified in the U.S. — and nearly three times more than the number of schools documented in Canada’s residential school system, according to that country’s Truth and Reconciliation Commission.

The investigation also has identified marked or unmarked burial sites at more than 50 schools across the Indian boarding school system. The department expects that number to go up as it continues to investigate.

The Federal Indian Boarding School Initiative was announced last summer by Interior Secretary Deb Haaland to investigate the history and lasting consequences of the schools. That announcement came as Indigenous groups across Canada confirmed the remains of more than 1,000 Indigenous children buried near former residential schools for Indigenous children there.

The U.S. Department of the Interior was “uniquely positioned” to undertake such an initiative, the secretary said at the time in a memorandum, because it had been responsible for operating or overseeing the boarding schools.

From 1819 through the 1960s, the U.S. implemented policies establishing and supporting Indian boarding schools across the nation to culturally assimilate Native American, Alaska Native and Native Hawaiian children, according to the department.

The schools forcibly removed children from their families, languages, religions and cultures. Many of those children endured physical and emotional abuse. Some died.

“The consequences of federal Indian boarding school policies, including the intergenerational trauma caused by forced family separation and cultural eradication, which were inflicted upon generations of children as young as 4 years old, are heartbreaking and undeniable,” said Haaland, a member of the Pueblo of Laguna and the first Native American to serve as a Cabinet secretary, at the news conference.

The Federal Indian Boarding School Initiative’s work included collecting records and information related to the department’s involvement in the Indian boarding school program and consulting with tribal nations, Alaska Native corporations and Native Hawaiian organizations.

The Roman Catholic Church and a number of Protestant denominations are beginning to investigate their own roles in those boarding schools, as many were sponsored or operated by religious organizations.

Several Catholic groups and Protestant denominations also have called for the United States to establish a Truth and Healing Commission similar to Canada’s Truth and Reconciliation Commission, which issued its final report on its own residential school system for Indigenous children in 2015.

They’re joined by lawmakers, who reintroduced the Truth and Healing Commission on Indian Boarding School Policies in the United States Act last year.

The act would create a commission to investigate, document and acknowledge the past injustices of U.S. boarding school policy. A U.S. commission also would develop recommendations for Congress to help heal the historical and intergenerational trauma passed down in Native families and communities and provide a forum for boarding school survivors to share their experiences.

“This is not new to us,” Haalaand said at the news conference. “It’s not new to many of us as Indigenous people. We have lived with the intergenerational trauma of federal Indian boarding school policies for many years. But what is new is the determination in the Biden-Harris administration to make a lasting difference in the impact of this trauma for future generations.”

This story will be updated.