Theodore McCarrick, center, greets Pope Francis in 2015 at the Cathedral of St. Matthew in Washington
CNN  — 

Pope Francis ordered a Vatican investigation last year into abuse allegations against US Archbishop Theodore McCarrick but is not yet releasing the results, the Vatican revealed Saturday.

“The Holy See will, in due course, make known the conclusions of the matter regarding Archbishop McCarrick,” the Vatican statement said.

US Catholics have been reeling in recent months from allegations that McCarrick, a former top American cardinal, sexually abused seminarians and an altar boy.

McCarrick, who has denied the accusations about the altar boy and not responded to the allegations about the seminarians, resigned from the College of Cardinals in July.

The allegations, as well as an explosive letter from a former papal diplomat, have raised serious questions among senior church leaders about why McCarrick was allowed to rise through the church’s ranks, as well as who knew about the accusations.

In its statement, the Vatican said it had ordered a preliminary investigation in September last year after it was informed by the Archdicoese of New York that a man had accused McCarrick of having abused him in the 1970s.

The investigation was conducted by the Archdiocese of New York, where the alleged abuse took place. The Archdiocese then sent its findings to the the Congregation for the Doctrine of the Faith in Rome, which acts as a watchdog division.

“In the meantime, because grave indications emerged during the course of the investigation, the Holy Father accepted the resignation of Archbishop McCarrick from the College of Cardinals, prohibiting him by order from exercising public ministry, and obliging him to lead a life of prayer and penance,” the statement said.

The investigation’s conclusions will be made known “in due course,” and the information gathered during the preliminary investigation will be combined with other Church records regarding McCarrick “in order to ascertain all the relevant facts, to place them in their historical context and to evaluate them objectively,” the statement said.

The archdiocese earlier said it had found the allegations against McCarrick to be “credible and substantiated” and that it had handed the accusation over to law enforcement.

“The Holy See is conscious that, from the examination of the facts and of the circumstances, it may emerge that choices were taken that would not be consonant with a contemporary approach to such issues. However, as Pope Francis has said: ‘We will follow the path of truth wherever it may lead,’” the Vatican statement said.

“Both abuse and its cover-up can no longer be tolerated and a different treatment for Bishops who have committed or covered up abuse, in fact represents a form of clericalism that is no longer acceptable.”

The US Catholic bishops’ conference last month issued a dramatic apology for the role of bishops in the church’s clergy sexual abuse scandal and announced new initiatives to hold abusive or negligent bishops accountable.

Francis has come under increasing pressure to act over the sexual abuse crisis that has engulfed the Catholic Church in countries around the world, with survivors complaining that the Vatican is moving at a “glacial” speed on the issue.

The Pope last month summoned the church’s top officials from across the world to the Vatican for a February meeting to discuss the problem.

In Saturday’s statement, the Vatican said Francis “renews his pressing invitation to unite forces to fight against the grave scourge of abuse within and beyond the Church, and to prevent such crimes from being committed in the future to the harm of the most innocent and most vulnerable in society.”

CNN’s Richard Allen Greene contributed to this report.