The First Nation took over the school's cemetery from the Catholic Church in the 1970s.

Earlier this month Cowessess started using ground-penetrating radar to locate unmarked graves. It was not immediately clear if all the remains are connected to the residential school.

Cowessess Chief Cadmus Delorme spoke at a virtual news conference Thursday morning.

"This is not a mass grave site. These are unmarked graves," Delorme said.

Delorme said there may have at one point been markers for the graves. He said the Roman Catholic church, which oversaw the cemetery,may have removed markers at some point in the 1960s.

He said it was not immediately clear if all of the unmarked graves belonged to children, but that there were oral stories within Cowesses First Nation about both children and adults being there.

Delorme said some 44,000 square metres of area were searched by technical teams from Saskatchewan Polytechnic, which the First Nation partnered with for the search.

Teams were unable to confirm if there were more remains, but said there were 751 "recorded hits" at the site and noted there could be more than one set of remains at each "hit." He said the penetrating radar work has a 10 to 15 per cent error rate.

Technical teams would be able to provide a verified number in the coming weeks, Delorme said.

Thursday's announcement marked "Phase 1" of the First Nation's search efforts, he said. The community would continue search efforts in the area based on oral history.

Last month the Tk'emlúps te Secwépemc First Nation in B.C. announced the discovery of a burial site adjacent to the former Kamloops Indian Residential School that preliminary findings indicate contains the remains of 215 children.

Delorme said the community wants to put names to the people in the graves in the coming months. He said the community would be treating the site "like a crime scene."

He said he would like to see a monument built at the site that includes the names of those identified.

'A crime against humanity': FSIN

FSIN Chief Bobby Cameron said Thursday that what happened was a "crime against humanity'' and that the findings were just the start in terms of finding unmarked graves in Saskatchewan.

"There will be hundreds more unmarked graves and burial sites located across our First Nations land at the sites of former Indian Residential Schools," Cameron said in a prepared statement.

"There are thousands of families across our Treaty territories that have been waiting for their children to come home. Saskatchewan had the highest number of residential schools and highest number of survivors."

He said the FSIN would work to get every site in Saskatchewan — schools, sanatoriums and other such locations — searched and victims in those locations identified.

Cameron called on all levels of government to support First Nations efforts in their efforts at those sites.