A sacred fire will be lit in Thunder Bay on Monday in honour of the 215 children who were found at the site of a former residential school in Kamloops, B.C.

The children's remains were discovered during a search of the grounds of the former Kamloops Indian Residential School. The search made use of ground-penetrating radar, and was organized by Tk'emlúps te Secwépemc First Nation.

In a Facebook post on the weekend, NAN Grand Chief Alvin Fiddler said he and Fort William First Nation Chief Peter Collins will light the sacred fire at 3 p.m. Monday.

The fire will be lit at the site of the former St. Joseph's Indian Residential School on Arthur Street in Thunder Bay.

The fire will burn for four days, and anyone who attends the ceremony is asked to wear orange.

In a statement issued Saturday, NAN Deputy Grand Chief Derek Fox offered condolences following the discovery of the remains.

"We are very saddened to learn that the final resting place of so many innocent children have been discovered at the Kamloops Indian Residential School," Fox stated. "Our thoughts and prayers are with the families of these youth and the entire Tk'emlúps te Secwépemc community. Even after all these years there are new tragedies of the residential school system coming to light."

"We commend the knowledge keepers and the families for their perseverance to uncover the truth behind the terrible loss of these young children," the statement reads. "This discovery shows how the legacy of the residential school system continues to impact the lives of residential school survivors and the families of those who never returned home."

The City of Thunder Bay also announced on the weekend that the flags at City Hall will be flown at half-mast from Monday to June 8, "to honour the lives of 215 children found in a mass grave at the site of a former residential school in Kamloops, B.C."

"The flags will remain lowered for one hour for every child whose life was lost, and 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 city said in a media release.