A mass grave containing the remains of 215 indigenous children, the youngest of them only 3 years old, has been found at a former residential school in Kamloops in western Canada.

In a statement, Chief Rosanne Casimir of the Tk'emlups te Secwépemc First Nation said the grave was confirmed last weekend with the help of ground-penetrating radar, and that more bodies may be found because there are more areas to search on the school grounds.

"We had a knowing in our community that we were able to verify. To our knowledge, these missing children are undocumented deaths," she said.

At least 150,000 children attended such schools in what a historic 2015 Truth and Reconciliation Commission described as a "culture of genocide" targeting Canada's indigenous people.

The Kamloops Indian residential school was established in 1890 as part of a cross-Canada network of such state-funded Christian schools.

By removing the children from their homes and communities, and forbidding them from speaking their native languages or performing their own cultural practices, the schools sought to forcibly assimilate the children into the colonially imposed Canadian society.

The children suffered physical, emotional and sexual abuse, and were used as forced labor. It is not known how many children died in the schools. The Truth and Reconciliation Commission calculated at least 3,201 residential school deaths, although the true figure will undoubtedly be considerably higher due to unreported deaths and destroyed files.

The remains of the 215 indigenous children are testimony to the "legacy of genocide toward Indigenous people," Terry Teegee, regional chief for British Colombia of the Assembly of First Nations, said on Friday.

Some Western countries, Canada included, like to preach to other countries about human rights affairs. They should review their pasts and correct their own wrongdoings, instead of pointing fingers at others.