The Associated Press has learned that a State Department review has found at least 20 instances of workers peeking at the passport files of high-profile Americans, including former Playboy playmate Anna Nicole Smith, over the past year.

That is far more than disclosed last week when U.S. officials discovered that workers had improperly snooped into the passport files of the three presidential candidates.

It's not yet clear if the other files were looked at improperly.

Although officials told AP that Smith's file appears to have been accessed on a legitimate request for information needed for her death certificate after she died in the Bahamas last year.