GENEVA -- UN human rights experts have urged Canadian authorities and the Catholic Church to conduct quick and thorough investigations into the discovery of a mass grave containing the remains of over 200 children at a British Columbia 'residential school' for indigenous children forcibly taken from their homes.

The Kamloops Indian Residential School, where the children's remains were found in May, had been run by the Catholic Church between late 19th century and the late 1960s, when the federal government took over until its closure in the 1970s.

It was part of the indigenous residential school system which, between 1831 and 1996, hosted over 150,000 children in 130 schools, many run by the Catholic Church or the federal government.

"The discovery of the remains of 215 children at the site of a defunct boarding school in British Columbia has rekindled discussion of a sinister time in Canada's history," The New York Times reported June 7.

The government-run boarding schools were set up for the forced assimilation of indigenous children, the BBC reported.

Canadian Prime Minister Justin Trudeau urged the Catholic Church to "take responsibility" for its role in indigenous residential schools.

"As a Catholic, I am deeply disappointed by the position that the Catholic Church has taken now and over the past many years," Trudeau told reporters.

The 2015 report of Canada's Truth and Reconciliation Commission determined that Aboriginal children were subjected to abuse, malnutrition and rape, and that at least 4,000 died of disease, neglect, accidents or abuse while at these schools.

"We urge the authorities to conduct full-fledged investigations into the circumstances and responsibilities surrounding these deaths, including forensic examinations of the remains found, and to proceed to the identification and registration of the missing children," said the UN experts who are appointed by the Human Rights Council.

The UN experts include Fabián Salvioli, Special Rapporteur on truth, justice, reparation and guarantees of non-recurrence; Francisco Cali Tzay, Special Rapporteur on indigenous peoples' rights; Mama Fatima Singhateh, Special Rapporteur on sale and sexual exploitation of children and other experts.

They further called on the Canadian government "to undertake similar investigations in all other Indigenous residential schools in the country."

They recalled the right of victims to know the full extent of the truth about the violations endured.

'CONDUCT CRIMINAL INVESTIGATONS'

"The judiciary should conduct criminal investigations into all suspicious death and allegations of torture and sexual violence against children hosted in residential schools, and prosecute and sanction the perpetrators and concealers who may still be alive," said the experts.

"Large scale human rights violations have been committed against children belonging to indigenous communities, it is inconceivable that Canada and the Holy See would leave such heinous crimes unaccounted for and without full redress."

The experts called on the Government of Canada to fully implement the recommendations contained in the Report of the Truth and Reconciliation Commission of 2015.

"For far too many years, victims and their families have been waiting for justice and remedy. Accountability, comprehensive truth, and full reparation must be urgently pursued," they said.

The UN experts urged the Catholic Church "to provide full access to judicial authorities to the archives of the residential schools run by the institution, to conduct prompt and thorough internal and judicial investigations into these allegations, and to publicly disclose the result of those investigations."

The experts have been in contact with Canada and the Vatican concerning the indigenous residential schools.

The discovery of the graves has given new impetus to Canada's debate on how to atone for its history of exploiting Indigenous people. "Many are asking how so many children could have wound up in that burial space," said The New York Times.