The Dallas County district attorney is investigating whether the Catholic Diocese of Dallas (search) has failed to report allegations of clergy sexual abuse to law enforcement officials.

The diocese declared in writing three years ago that no one in the ministry had violated any state law, but two recent cases have made prosecutors suspicious of that claim, Rachel Horton, spokeswoman for District Attorney Bill Hill, told Monday night's online edition of The Dallas Morning News (search).

Sunday, a pastor in Rockwall who had been accused in the early 1990s of sexually harassing boys at jobs in Dallas and Plano resigned. The pastor's accusers said they never saw any indication that the diocese investigated the allegations or reported them to authorities.

In the other case, police in Grand Prairie arrested a pastor on child pornography possession charges last week.

Both priests have declined to comment.

Bronson Havard, a spokesman for Bishop Charles Grahmann, said in an e-mail that "we welcome the DA's help and will cooperate fully with him."

Grahmann has barred about 10 priests from ministry because of sexual abuse. The diocese and its insurers have paid tens of millions of dollars to settle claims. Two of the priests have been prosecuted and sent to prison by the DA's office.

The group Survivors Network of those Abused by Priests (search) said the Dallas investigation is the first involving clergymen who were on duty after U.S. bishops adopted national "zero tolerance" reforms in 2002.

"It's groundbreaking," SNAP leader David Clohessy said. "So many prosecutors want to believe the church has learned its lesson."