Updated: The Los Angeles Times has a more extensive story.
Addendum. NYT has more, including reaction from the diocese and Cardinal Mahony.
Federal authorities are investigating the Catholic Archdiocese of Los Angeles to see whether top church officials tried to cover up the sexual abuse of minors by priests, said a person familiar with the matter.
A federal grand jury has issued subpoenas and begun calling witnesses in the probe, which began late last year, said this person. The investigation is still in its early, fact-gathering stage, and it isn't known whether any criminal charges will result.