ROME — The Vatican said Friday it has decided to launch a preliminary sex abuse investigation into a prominent French cardinal after he admitted to having behaved in a “reprehensible way” with a 14-year-old girl 35 years ago.

Vatican spokesman Matteo Bruni said a search was under way to find a lead investigator with the “necessary autonomy, impartiality and experience.”

Cardinal Jean-Pierre Ricard, the retired archbishop of Bordeaux and a former president of the French bishops’ conference, confessed to the abuse in a letter last week while French bishops were meeting at their annual assembly in Lourdes. The revelation further sparked outrage within the French Catholic Church, which has been reeling over revelations of decades of abuse and cover-ups detailed in a groundbreaking report last year.

Marseille prosecutors announced this week they had opened an investigation into Ricard for alleged “aggravated sexual assault” but that “no complaint” had yet been filed against the cardinal.

The decision by the Vatican to go ahead and open its own investigation while the French criminal probe was under way was unusual and suggested the seriousness of the matter for Rome. A cardinal since 2006, Ricard is a high-ranking member of several important Vatican offices. Most significantly, he is a voting member on the Vatican’s Dicastery for the Doctrine of the Faith, meaning he has been involved in adjudicating other clergy sex abuse cases for years.

There was no word on whether he would be suspended or removed from his Vatican member posts pending the investigations. Ricard said in his letter he was placing himself at the discretion of church and civil authorities.

In announcing their investigation, Marseille prosecutors said they first received a report about Ricard in October from the Nice bishop, who reported having received a letter from the parents of the alleged victim who were outraged that Ricard had been appointed by the Vatican to a team investigating a Catholic association that runs foster homes.

When Nice Bishop Jean-Philippe Nault confronted Ricard about the parents’ letter, the cardinal “admitted to this prelate that, more than 40 years ago, he had ‘kissed’ the daughter of this couple, whose religious marriage he would later have celebrated,” Marseille prosecutors said.

Sister Véronique Margron, head of the conference of religious orders in France, told France’s La Croix Catholic newspaper this week that the victim herself had twice written to Pope Francis — once five years ago, and again in May-June of this year after she didn’t receive a response.

Bruni didn’t respond when asked if the pope received either of the letters. Bruni said the decision to open the preliminary investigation into Ricard was made “to complete the examination of what happened, given the elements that have emerged in recent days and the declaration given by the cardinal.”

Francis has vowed “zero tolerance” for clerics who abuse and in recent years has removed several bishops and a few cardinals for abuse and cover-ups. But he had a big learning curve on abuse and initially botched some cases, trusting the words of clerics over the victims.

Last year, France’s Sauve report into Catholic abuse estimated that 330,000 children in France were sexually abused over the past 70 years by some 3,000 priests and other people involved in the church and that the crimes were covered up in a “systemic manner” by the church hierarchy.