"The history of many metis, born of a Congolese, Rwandan or Burundian mother and a white father (serving) in one of these countries, is an obscure episode of Belgian colonization," the bishops' conference said in an April 26 statement.

"These children were long designated pejoratively as 'mulattoes,' while the colonial authorities, both civil and ecclesiastical, considered them a real problem. ... We express regret for the part played in this by the Catholic Church."

The statement was published after an official church apology was delivered by Bishop Johan Bonny of Antwerp during an April 25 symposium in the Belgian Senate.

It said many mixed-race people had been placed in orphanages and boarding schools run by Belgian religious orders, permanently cutting them off from their families.

"This was the beginning of a sorrowful separation and long search," the bishops said. "All the good intentions and motivations behind their placement in institutions led to an alienation, which was even greater given their origin and true identity."

While colonial segregation was in force, up to 20,000 people were believed born to white fathers and African mothers in Belgian-ruled Congo, Rwanda and Burundi. Many were forcibly fostered by Catholic orders and sent to Belgium for adoption in 1959-62 without their mothers' consent.

In 2016, the Metis de Belgique association, representing mixed-race adoptees, appealed for state recognition of their mistreatment and discrimination.

The bishops' conference statement said all organizations with historical documents, including birth and marriage certificates, were asked to make them available to researchers, and it said the church counted on the Belgian government to find solutions.

Jesuit Father Tommy Scholtes, spokesman for the bishops' conference, said information was being sought from church groups in Rome and Africa for help in establishing the true identity of mixed-race citizens and would be coordinated by the Belgian church's family commission.

"It took till last year for this issue to be raised – and the church wishes to apologize for the whole of society, not just for itself," Msgr. Scholtes told Catholic News Service April 27.

"Although no firm statistics are available, we know a lot of these children came from Catholic missions, who did good charitable work but failed to preserve (the children's) identity," he added.