MONTREAL, Canada - Pope Francis has tasked a retired judge with investigating allegations that a Canadian cardinal, who is a close advisor to the pontiff, sexually assaulted a teenage girl in the 1980s, according to letters seen by AFP Monday.

Cardinal Gerald Lacroix, the 66-year-old archbishop of Quebec, is facing claims of sexual assault dating back to 1987 and 1988, when the victim was 17, as part of a class action suit against more than 100 priests in the archdiocese.

Lacroix has been Quebec's archbishop since 2011 and a cardinal since 2014. Since last year, he has served on the pontiff's Council of Cardinal Advisors, which meets regularly at the Vatican.

According to a February 8 letter from the pontiff, retired judge Andre Denis is to determine, based on "an investigation of the facts, circumstances and attributability of the alleged offense," if there is enough evidence to warrant a canonical trial.

The probe will not determine whether Lacroix is guilty.

Denis has previously studied thousands of sexual misconduct allegations against the Church dating as far back as the 1940s, and authored a report that confirmed or substantiated dozens of claims.

He noted in a letter to the plaintiff's lawyer, in which he says he plans to meet with witnesses starting on March 18, that he will send his findings in a report to Pope Francis.

Lacroix has denied the accusations. In January he said he would pause his duties until the situation is cleared up, but he was present for the last meeting of the Council of Cardinal Advisors at the Vatican in early February.

The class action suit features testimony from 147 people who claim they were sexually assaulted by more than 100 priests in the archdiocese, some of them high-ranking clergy, according to court documents.

Pope Francis has made combatting sexual assault in the Catholic Church one of the main missions of his papacy, and insisted on a "zero tolerance" policy following multiple wide-reaching scandals. — Agence France-Presse