Six Catholic dioceses in Illinois have failed to disclose the names of at least 500 priests accused of sexual abuse, the state's attorney general announced Wednesday. Illinois Attorney General Lisa Madigan said the preliminary findings are the result of a monthslong investigation that began in August after a grand jury report in Pennsylvania found 300 "predator priests" in that state.

"By choosing not to thoroughly investigate allegations, the Catholic Church has failed in its moral obligation to provide survivors, parishioners and the public a complete and accurate accounting of all sexually inappropriate behavior involving priests in Illinois," Madigan said in a statement. "The failure to investigate also means that the Catholic Church has never made an effort to determine whether the conduct of the accused priests was ignored or covered up by superiors."

The Illinois dioceses have publicly identified 185 priests who have been "credibly" accused of sexually abusing children, Madigan said. But the dioceses had received accusations against at least 500 additional priests, and Madigan said many of those accusations were not thoroughly investigated or brought to authorities.

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"Among the common reasons the dioceses have provided for not investigating an allegation is that the priest or clergy member was deceased or had already resigned at the time the allegation of child sexual abuse was first reported to the diocese," Madigan's office said.

In a statement to the Chicago Tribune, Chicago Cardinal Blase Cupich said: "I want to express again the profound regret of the whole church for our failures to address the scourge of clerical sexual abuse."

Madigan said her office had spoken to all six dioceses in the state and met with bishops, lawyers and diocesan representatives.

The Pennsylvania grand jury released findings from a two-year-long investigation into sexual abuse by priests in the state. It relayed the findings of more than 1,000 victims, but said there could be thousands more victims. The report said the cover-up to protect church leaders went all the way up to the Vatican.