Three more women have come forward alleging they were sexually abused by a monk on a Pembrokeshire island in the 1970s and 1980s.
A total of 11 women now claim Father Thaddeus Kotik abused them on Caldey Island when they were children.
A letter seen by BBC Wales shows Kotik's abuse was reported to abbot Brother Robert O'Brien in 1990, but not to police.
Dyfed-Powys Police said it received reports of the abuse in 2014 and 2016.
The force investigated but could not prosecute as Kotik died in 1992.
Six women have already been paid compensation in an out-of-court settlement by Caldey Abbey following the sexual abuse claims.
But journalist Amanda Gearing, who has spoken to victims, said three more women now claim to have been sexually assaulted by Kotik.
One woman who reported her case to police on Monday told the Guardian she broke down and was unable to sleep for 36 hours after reading about Kotik's abuse of others.
She said her abuse was "low level compared with others" but it happened when she was sat next to Kotik on a bench.
"He put his hand up my top. Then his hand went up my back and under my arms. I squirmed away from him and walked away. I didn't go near him after that," she said.
Another woman told the Guardian she and her two sisters were abused by Kotik, but claimed there was pressure by both the church and family for victims to "shut up".
Kotik befriended families who regularly visited the island. After gaining the trust of parents he would babysit the children and sexually abuse them, court papers have suggested.
One of them, who has already spoken out about what happened, said she "bitterly regrets" her abuser was never jailed.
There are fears there could be more victims and calls have been made for an independent inquiry by the Minister and Clergy Sexual Abuse Survivors group.
In the letter seen by BBC Wales, Brother Robert, who died in 2009, said Kotik's behaviour was known about in the monastery, which attracts tourists to the small island.
"The conduct of Father Thaddeus Kotik was a serious heartache to me and I rebuked him very sharply, urging on him the welfare of these little ones, warning him of the severe penalties this country rightly imposes," he wrote.
Brother Robert was also aware of the methods Kotik used.
"He likes to 'spoil' as much as 'be spoilt' so won their friendship with biscuits and sweets. When I began to be anxious I forbade him to go to the (the victim's) home," the letter continued.
"I summoned Father Thaddeus and warned him of the wrong he was doing the children. He was very contrite, assured me it had gone no further.
"I tried to keep an eye on his goings and comings. I think he did improve a while.
"I believed that it was touches through their clothes and sadly touches by them on his body but again through his clothes. It is possible though, I hope not, that Fr Thaddeus did abuse… more seriously.
"I feel fairly sure I can prevent any repetition with the young children on the island."
Caldey is a small island less than a mile off the Pembrokeshire coast near Tenby, and a Celtic monastery was first established there in the 6th Century.
The current abbey was built in 1910 by Anglican Benedictine monks and was passed to the Cistercian order in 1929.
BBC Wales has attempted to contact Caldey Abbey.