The Legion of Christ, a Catholic congregation, said on Friday it had found nine of its priests guilty of sexual abuse of minors including its disgraced founder and one who assaulted a novice in the United States.
The Legion's reputation was already clouded by earlier revelations about Marcial Maciel, who set up the group in Mexico in 1941 and was accused of abusing eight young seminarians as well as fathering a child.
Father Sylvester Heereman, the group's acting general director, said the investigations had shown up a "painful and horrifying reality" and emphasised his commitment to tackling abuse in the conservative group.
It said two of the priests had been defrocked and seven had "sanctions imposed on their life and ministry".
Legion officials were unable to say whether any of these cases were being investigated by civil authorities, although some date back decades and the crimes may have expired under statutes of limitations.
A total of 35 priests were accused in the investigation, which was conducted under Canon Law.
The Legion found abuse "did not take place" in 14 cases, while 10 more were still being investigated and two were ex-priests and therefore not prosecutable.
One case uncovered was that of Father William Izquierdo, a former teacher at a Legion facility in Connecticut in the United States between 1982 and 1994 who "sexually abused a novice under his care".
The group said Izquierdo would not be punished but was now 85 and in "an advanced state of dementia" and in any case had not exercised his ministry since 2008.
Izquierdo will be moved "to an assisted living facility where he will receive proper treatment," it said.
It said there was another allegation against Izquierdo and Luis Garza, the Legion's North American territorial director, encouraged more victims to come forward.
The congregation said that four percent of the 1,133 priests ordained in its history had been accused of sexual misconduct and one percent had been found guilty.
The Legion of Christ has been in crisis since the first revelations about the double life of Maciel, who was supported by late pope John Paul II and died in 2008.
The Vatican has repeatedly promised to crack down on child sex abuse by clergymen and on Thursday Pope Francis said he was setting up a special commission to protect children and offer pastoral care for victims.
It has also, however, refused to answer questions from a UN committee on child protection on its abuse investigations, saying it is not "legally competent", in cases where priests are subject to national laws.