The Pope is to study a report into the Tuam mother and baby home given to him on his Irish visit.
The two-day trip was dominated by the issue of clerical sex abuse - with the Pontiff calling on the Irish people to forgive those in the church who covered it up.
Children's Minister Katherine Zappone was one of the first to meet Pope Francis when he arrived in Ireland on Saturday - highlighting the controversy of the mother and baby home in Tuam.
The Pope told reporters on the papal flight to Rome last night that Ms Zappone told him about the discovery of mass graves of children – and that the church has something to do with it.
Francis told reporters: "I had never heard of these mothers, they call it the laundromat of women where an unwed woman is pregnant and goes into these hospitals, I don’t know what they call them, schools, run by the nuns and then they gave children to the people in adoption."
He confirmed he has been sent a memo on the issue – but had yet to study it.
Yesterday, the Pontiff acknowledged that senior members of the church kept quiet about child sexual abuse – calling on those at the mass in the Phoenix Park to forgive them.
During his 36-hour trip, the 81-year-old also meet with survivors of abuse, visited the Capuchin day centre for the homeless along with a brief visit to Knock Shrine where 45,000 came out to see him.
Abuse survivor and campaigner Colm O'Gorman who organised the Stand 4 Truth event in Dublin yesterday says people know the truth of what happened within the Catholic Church.
"We know what happened in the Magdalene Laundries, we are investigating the mother and baby homes, we've had the Ferns, Murphy and Cloyne reports. We know what happened," said Mr O'Gorman.
"We know the cover-up. We know who's responsible for it. We know it was clergy at every level - it was bishops, it was cardinals, it was popes.
"We also know that the State colluded in that and the State has taken some significant responsibility with that. The church hasn't.
"But we don't need them to tell us the truth. We know it."
Mr O'Gorman also said that Irish people need a response from the Pope on the truth of clerical abuse.
"He holds an office of extraordinary power and responsibility and he needs to act with integrity and acknowledge the damn truth.
"Twenty years I have been asking three popes to tell the truth.
"I thought Francis might do it but he has doubled down here and he has wrapped up words that if you put them together might sound significant - words like cover-up and crime and accountability - but utterly disconnected and just thrown and peppered across statements."