Pope Francis has expressed his pain over the discovery in Canada of the remains of 215 Indigenous students of church-run boarding schools, and pressed religious and political authorities to shed light on “this sad affair”.

But the pontiff did not offer the apology sought by the Canadian prime minister.

Francis, in remarks to faithful gathered in St Peter’s Square, also called on the authorities to foster healing but made no reference to prime minister Justin Trudeau’s insistence, two days earlier, that the Vatican apologise and take responsibility.

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

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

Ground-penetrating radar was used to confirm the remains of the children at Kamloops Indian Residential School in Kamloops, British Columbia, last month. It was Canada’s largest such facility and was operated by the Catholic church between 1890 and 1969.

“I am following with pain the news that arrives from Canada about the upsetting discovery of the remains of 215 children,” Francis said in his customary Sunday noon remarks to the public.

“I join with the Canadian bishops and the entire Catholic church in Canada in expressing my closeness to the Canadian people traumatised by the shocking news.

”This sad discovery adds to the awareness of the sorrows and sufferings of the past.”

Mr Trudeau on Friday condemned the church for being “silent” and “not stepping up”, and called on it to formally apologise and to make amends for its prominent role in the system of church-run Indigenous boarding schools.

He said that when he met Francis at the Vatican in 2017 he had asked him to “move forward on apologising” and on making records available, but “we’re still seeing resistance from the church, possibly from the church in Canada”.

Chief Rosanne Casimir of the Tk’emlups te Secwepemc First Nation in British Columbia has said her nation wants a public apology from the Catholic church. The Missionary Oblates of Mary Immaculate, which ran nearly half of Canada’s residential schools, has yet to release any records about the Kamloops school, she said.

Francis’s comments spoke of healing but not of apology.

“May the political and religious authorities continue to collaborate with determination to shed light on this sad affair and to commit humbly to a path of reconciliation and healing,″ he said.

“These difficult moments represent a strong call to distance ourselves from the colonial model and from today’s ideological colonising and to walk side by side in dialogue, in mutual respect and in recognising rights and cultural values of all the daughters and sons of Canada.

“Let’s entrust to the Lord the souls of all those children, deceased in the residential schools of Canada. Let us pray for the families and for the indigenous Canadian communities overcome by sorrow.”

The United, Presbyterian and Anglican churches have apologised for their roles in the abuse, as has the Canadian government, which has offered compensation.

Among the many recommendations of a government-established Truth and Reconciliation Commission was a papal apology.