WASHINGTON — A federal investigation of unauthorized snooping into government passport files has found evidence that such breaches might be far more common than previously disclosed and urged an overhaul of the program's management.

A report issued Thursday by the State Department's inspector general found "many control weakness" in the department's administration program, including what investigators said was a lack of sound policies on accessing the electronic records, training staff and disciplining those who broke privacy rules.

The investigation was launched in March after it was disclosed that government workers and contract employees had snooped in the files of Sen. Hillary Rodham Clinton, Sen. Barack Obama and Sen. John McCain.

To assess the extent of the breach, investigators assembled a sample of 150 famous Americans, including athletes, politicians and entertainers, and examined how many times their files in a government database were viewed over six years. Of the 150 celebrities, the files of 85 percent were accessed at least once; the files were accessed a total of 4,148 times. Nine files were opened more than 101 times.

The report did not try to assess which of the "hits" were unauthorized, but it said that the 85 percent rate "appears to be excessive."

State Department officials did not identify the celebrities whose files were included. More than 20,500 federal and contract employees have access to the records database, including State Department staff and officials involved in investigations, security assessments and other analyses, the report said.

Five persons have been fired. Officials said they were continuing to investigate whether additional personnel had violated procedures or federal privacy laws and deserved punishment.

Michael Kirby, a senior official in the Bureau of Consular Affairs, said officials "are reviewing the circumstances under which people looked at these records, and we will take action."

The initial disclosure of snooping on the presidential candidates' files raised questions about whether administration officials might have been looking for embarrassing information for partisan political reasons. But officials say they have found no such evidence.

Sen. Joseph R. Biden Jr., D-Del., chairman of the Senate Foreign Relations Committee, called the report "deeply disturbing" and urged Secretary of State Condoleezza Rice to ensure that the deficiencies were corrected. The files flap prompted Rice to apologize to the presidential candidates.