The Canadian flag at the Peace Tower in Ottawa was lowered to half-mast on Sunday, following the report of the discovery of the remains of 215 children at the site of a former residential school in Kamloops, B.C.

The Department of Canadian Heritage said flags at all federal buildings and establishments across Canada would be lowered until further notice "in memory of the thousands of children who were sent to residential schools, for those who never returned and in honour of the families whose lives were forever changed."

The bodies of the 215 children were discovered during a search of the grounds of the former residential school, the Tk'emlúps te Secwépemc First Nation announced Thursday. A statement from the First Nation said that the missing children, some as young as three years old, were undocumented deaths.

Tk'emlúps te Secwépemc Kukpi7 (Chief) Rosanne Casimir told CBC's Daybreak Kamloops on Friday that more than symbolic gestures are needed to address the tragedy.

"It's all good and well for the federal government to make gestures of goodwill and support regarding the tragedy," Casimir said. "There is an important ownership and accountability to both Tk'emlúps te Secwépemc and all communities and families that are affected. And that needs to happen and take place."

Flags across the country have also been lowered or will be lowered in honour of the children — including at the British Columbia and Manitoba legislatures as well as in Montreal, Edmonton and across much of Ontario.

Ottawa Mayor Jim Watson said on Twitter on Sunday that flags at Ottawa's city hall would remain at half-mast "for one hour for every child whose life was taken."

As well, vigils and memorials were held in cities and towns across the country over the weekend, including outside the Alberta and Ontario legislatures and at Toronto's Nathan Philip Square. At some memorials, rows of tiny shoes served as visual reminders of the young lives that were lost.

B.C. Premier John Horgan issued a statement Friday on the discovery.

"This is a tragedy of unimaginable proportions. And it is a stark example of the violence the Canadian residential school system inflicted upon Indigenous peoples and how the consequences of these atrocities continue to this day," he said.

A National Indian Residential School Crisis Line has been set up to provide support for former students and those affected. Emotional and crisis referral services can be accessed by calling the 24-hour national crisis line: 1-866 925-4419.