A former high-ranking Prince George's County schools official arrested in January on charges that she helped hide money for an illegal drug operation based in Virginia now faces an additional charge of witness tampering, according to an indictment made public yesterday in federal court.

Pamela Y. Hoffler-Riddick, 44, appeared in federal court in Norfolk as a grand jury returned an indictment accusing her of corruptly influencing and attempting to influence the testimony of a government witness. The indictment included scant details; supporting documents describing the alleged crime remained under court seal.

Hoffler-Riddick is scheduled to enter a plea on the witness-tampering charge Wednesday, said a U.S. Justice Department official based in Virginia familiar with the case. In February, she said she was not guilty of money laundering.

The new indictment adds to the challenge Hoffler-Riddick faces in the multi-state drug-trafficking case in which prosecutors allege she helped launder about $50,000 in profits starting in the late 1990s. Her trial on five money-laundering counts, each of which carries a maximum prison term of 20 years, is scheduled to begin this summer. The tampering charge carries a penalty of up to 10 years in prison.

"Witness tampering is a serious offense," Dean Boyd, a spokesman for U.S. Immigration and Customs Enforcement, said yesterday in a statement. "If the charge of attempting to influence the testimony of a witness is proven accurate, it's a very troubling development in this case."

The Justice official, who cited grand jury secrecy rules in requesting anonymity, said prosecutors gleaned evidence of witness tampering from an exchange of e-mails between Hoffler-Riddick and a witness in the larger drug case. The indictment said the alleged crime occurred in February and March.

Hoffler-Riddick's attorney, David W. Bouchard, did not return phone calls seeking comment. He has previously described his client as an innocent figure unjustly ensnared in a broad federal case because of a relationship she had with a man accused of being near the center of a drug-trafficking ring.

Hoffler-Riddick has been free on bond since her arrest and initial arraignment in early February. She surrendered yesterday to federal authorities before the hearing and was released afterward.

Until January, Hoffler-Riddick was a regional assistant superintendent, overseeing 39 schools in a wide swath of Prince George's, including high schools in Capitol Heights, Suitland, Largo, Springdale and Forestville. With 28,000 students in her zone, Region III, Hoffler-Riddick's position was comparable to the superintendency of an entire school system in a small or mid-size county.

Hoffler-Riddick's supporters have described her as an energetic, passionate and innovative educator with expertise in school accountability measures and teaching the disadvantaged. Some parents have sought to raise money for her defense.

Hoffler-Riddick began working for the Prince George's system in August 2003 and was placed on administrative leave in February, school spokesman John White said. She was not paid during most of that leave, he said. Her employment ended at the close of the school year.

Before coming to Prince George's, she held various school administration positions in Montgomery County, Baltimore and Norfolk.

The U.S. attorney's office for the eastern district of Virginia, which is prosecuting the case, would not comment on yesterday's development.

Staff writer Jerry Markon contributed to this report.