Altoona - Two Roman Catholic bishops who led a Pennsylvania diocese helped cover up the sexual abuse of hundreds of children by over 50 priests or religious leaders over a 40-year period, according to a grand jury report issued on Tuesday.The report on the Altoona-Johnstown Diocese was based partly on evidence from a secret diocesan archive uncovered through a search warrant executed last year, said Pennsylvania Attorney General Kathleen Kane."These predators desecrated a sacred trust and preyed upon their victims in the very places where they should have felt most safe," Kane said in a statement.No criminal charges are being filed because some abusers have died, the statute of limitations has expired and, in some cases, victims are too traumatised to testify, she said.The report is especially critical of Bishops James Hogan and Joseph Adamec. Hogan, who led the diocese from 1966 to 1986, died in 2005. Adamec, who succeeded him, retired in 2011.The report said Hogan covered up abuse allegations by transferring offending priests, including by sending one accused clergyman to a school for boys. It said Adamec or his staff threatened some alleged victims with excommunication.One diocesan official under Hogan, Monsignor Philip Saylor, told the grand jury that church officials held such sway that "the police and civil authorities would often defer to the diocese" when priests were accused of abuse, the report said.Payout chartThe report said Adamec created a "payout chart" to help guide how much victims would receive from the church. Victims fondled over their clothes were to be paid $10 000 to $25 000; fondled under their clothes or subjected to masturbation, $15 000 to $40 000; subjected to forced oral sex, $25 000 to $75 000; subjected to forced sodomy or intercourse, $50 000 to $175 000.In a court filing, Adamec's attorney said the accusations against the 80-year-old are unfounded. Adamec required 14 priests accused under his watch to undergo psychiatric evaluation, the filing said. Nine were suspended or removed from ministry, and the five who were reinstated never re-offended, his attorney wrote.The current bishop, Mark Bartchak, is not accused of wrongdoing. He recently suspended a handful of priests named as alleged abusers in the report, though the grand jury said it remains "concerned the purge of predators is taking too long".Bartchak, issued a statement saying he deeply regrets "any harm that has come to children". He said the diocese will continue co-operating with authorities.The clergy sex abuse crisis erupted in 2002, when The Boston Globe persuaded a judge to unseal files from the Boston Archdiocese in the case of a paedophile priest who had been transferred by bishops from parish to parish without warning parents or civil authorities. The scandal then spread nationwide as Catholics and others demanded to know the full scope of wrongdoing.Dioceses across the country have been forced to release thousands of internal files on accused priests.The US Conference of Catholic Bishops estimates that American dioceses have paid nearly $4bn since 1950 to settle claims with victims.