VANCOUVER, British Columbia — Canadian Prime Minister Justin Trudeau says his "heart breaks" after the discovery of more unmarked graves on the grounds of an Indigenous residential school in the southern Gulf Islands off the British Columbia coast.

The Penelakut Tribe says more than 160 undocumented and unmarked graves have been found on the site of the former Kuper Island Indian Industrial School.

"I recognize these findings only deepen the pain that families, survivors and all Indigenous peoples and communities are already feeling as they reaffirm truth that they have long known," Trudeau said during a news conference Tuesday in Ottawa.

"To members of the Penelakut Tribe we are here for you. We cannot bring back those who are lost but we can and will continue to tell the truth," Trudeau said.

The Penelakut Tribe have issued a letter saying the graves were found on the grounds of the former residential school on what is now known as Penelakut Island between Vancouver Island and mainland B.C., about 78 miles (126 kilometers) southwest of Vancouver.

"We understand that many of our brothers and sisters from our neighboring communities attended the Kuper Island Industrial School," said the letter from Chief Joan Brown. "We also recognize with a tremendous amount of grief and loss, that too many did not return home."

The Kuper Island Indian Industrial School was operated by the Roman Catholic Church from 1890 until 1969, when the federal government took it over. The school was closed in 1975 and the building was demolished in the 1980s.

Trudeau said the federal government will work with Indigenous people to fight discrimination and systemic racism.

Close to 1,000 unmarked graves have been discovered at former residential school sites in British Columbia and Saskatchewan over the last several months.

In July, ground-penetrating radar found 182 human remains close to a former residential school in Cranbrook, B.C., 524 miles (843 kilometers) east of Vancouver.

Just a week earlier, the Cowessess First Nation, located about 85 miles (135 kilometers) east of the Saskatchewan capital of Regina said investigators found "at least 600" unmarked graves at the site of a former Marieval Indian Residential School.

In May, the remains of 215 children, some as young as 3 years old, were found buried on the site of what was once Canada's largest Indigenous residential school near Kamloops, B.C., 220 miles (354 kilometers) east of Vancouver.

From the 19th century until the 1970s, more than 150,000 Indigenous children were forced to attend state-funded Christian schools, the majority of them run by Roman Catholic missionary congregations, in a campaign to assimilate them into Canadian society.

The Canadian government has admitted that physical and sexual abuse was rampant in the schools, with students beaten for speaking their native languages.

Two New Democratic Party Members of Parliament have demanded the federal government investigate allegations of "crimes against humanity" in residential schools.