Madonna was spotted at the Kabbalah Centre, accompanied by her boyfriend Brahim Zaibat.
A supervisor with the Palos Verdes Estates Police Department, which had led a criminal probe into the handling of the housebound widow's affairs, said the department turned over files concerning her longtime business manager, John E. Larkin, to federal agents last month.
Sgt. Steve Barber declined to name the agency but said its focus was "financial activities" involving the 88-year-old heiress, Susan Strong Davis, and Larkin, a veteran Hollywood business manager who helps oversee the Kabbalah Centre's money.
A spokesman for the center, which has said it is cooperating with the IRS, declined to comment.
A lawyer for Larkin declined to comment on the new federal role in the Davis investigation but insisted Larkin had done nothing wrong.