After the discovery of unmarked graves in two separate indigenous residential schools in Canada, a local tribe said on Wednesday that additional 182 such graves were found in a third school.

From the grounds of the school, experts unearthed and identified the remains of pupils of children aged between seven to 15 using ground-penetrating radar mapping technology, reported AFP.

The remains were found in St Eugene’s Mission School in British Columbia’s Cranbrook, according to a statement from the Lower Kootenay Band.

The grim development follows the discovery of remains of 215 children in unmarked graves at the former Kamloops Indian Residential School in British Columbia in May and 751 more unmarked graves at another school in Marieval in Saskatchewan last week.

The Lower Kootenay Band said a search of the Cranbrook site, where the Catholic Church operated a school on behalf of the federal government from 1912 until the early 1970s, was started last year.

Some of the graves were as shallow as three to four feet deep, it said.

They are believed to be the remains of members of bands of the Ktunaxa nation, which includes the Lower Kootenay, and other neighboring indigenous communities.

Last Friday, Prime Minister Justin Trudeau apologized for the “harmful government policy” of indigenous assimilation.

Around 150,000 children from the Indian, Inuit and Metis communities lost their cultural spirit after being forcibly enrolled in such schools. The children were victims of sexual and physical abuse from the school staff, reported AFP.

The death of these children, which is being labelled as Canada’s “cultural genocide“, was attributed to disease and neglect on the part of the school, AFP reported quoting a commission that investigated the deaths.