A big political donor of Sen. Robert G. Torricelli (D-N.J.) was indicted Friday and accused of working with an aide to shred 10 bags of documents and delete computer files to obstruct a federal investigation.

David Chang, 55, who owns commodity trading companies in New Jersey, also is charged with misleading a witness before he testified to a federal grand jury and with instructing an aide to lie.

Part of the grand jury probe dealt with an $11,000 check from one of Chang's companies, Bright & Bright Corp. A lawyer who pleaded guilty to campaign finance charges in May said he helped Chang illegally funnel that money to Torricelli's 1996 campaign.

Torricelli has not been charged and has said he was unaware when unlawful donations were made and that the money since has been donated to charity.

Chang's former aide Audrey Yu, 31, was indicted last month on charges that she lied to a grand jury. The indictment returned Friday adds Chang as a defendant and charges him and Yu with conspiracy, obstructing justice and two counts of witness tampering.

The indictment does not name the witnesses but said the man misled by Chang and Yu was Bright & Bright's chairman. At the time, the chairman was a retired admiral, Daniel J. Murphy, who was chief of staff for George Bush when Bush was vice president, and a deputy director of the CIA.

Messages left for Yu's lawyers were not immediately returned.

Chang attorney David Schertler said his client is not guilty. He said the Justice Department has taken a "low-level felony allegation" about campaign finance "and they've blown it out of proportion and attempted to create crimes where there aren't any because of the highly charged atmosphere around campaign finance contributions."

Justice Department spokesman Myron Marlin could not immediately comment on why no campaign finance charges were brought against Chang.

The indictment followed nearly three years of investigation. Government agents spent at least four months examining Bright & Bright's garbage, according to court papers filed by the FBI.

Chang was listed by Mother Jones magazine as one of the top 400 donors during the 1997-98 election cycle, with contributions of $41,586 to candidates and organizations of both parties.

He was linked several years ago to the illegal donations that toppled former House member Jay Kim (R-Calif.). Kim was sentenced to probation. Chang cooperated with federal authorities and was not charged.