SAN DIEGO -- A newly released audit shows the San Diego County Treasurer-Tax Collector's Office improperly withheld about $8 million in overpayments and repeatedly failed to fix problems in how the office is run, it was reported Saturday.

The $73,000 audit completed in March by the New York auditing firm Kessler International was made public yesterday in response to a California Public Records Act request filed by The San Diego Union-Tribune.

At least two other independent audits dating to 2005 and an internal county audit completed in January 2008 identified similar problems in the office, the newspaper reported.

Treasurer-Tax Collector Dan McAllister, who is seeking a third four-year term in June, is running unopposed so far. He declined a request by the Union- Tribune to answer questions about the audit.

A two-page statement McAllister issued said transparency and accountability play a key role in his office, and that his department has adopted 97 percent of the recommendations made by auditors.

"These are moneys that rightfully belong to the people, and we simply want to give it back before the moneys are turned over to the county," McAllister wrote.

In the most recent audit, records in the tax collector's office were found to have been altered and deleted without explanation, computer systems were not properly secured and transactions were wrongly recorded or not logged, the Union-Tribune reported.

Auditors said office staffers and information technology contractor Northrop Grumman refused to turn over some records and denied that other documents existed, although they were discovered later.

"Kessler uncovered many discrepancies, irregularities and user errors during the audit, including the deletion of data, which is an indication that fraud may have occurred," the report said. "Based on the above, Kessler concludes that data integrity was compromised and the potential for fraud exists."

In addition to collecting and recording taxes assessed on nearly 1 million parcels across the county, the Treasurer-Tax Collector's Office oversees a countywide investment pool worth almost $6 billion.

McAllister was swept into public office in November 2002 after his predecessor, Bart Hartman, was accused of sexual harassment and other professional transgressions. The county later settled a sexual-harassment claim for $100,000.