A second former aide to Sacramento Mayor Kevin Johnson is now the focus of a Police Department inquiry into the use of a city-issued credit card, officials said Thursday.

Keith Hart, hired by Johnson as the city's chief service officer in July 2010, is the subject of a Police Department probe, said Sacramento police spokesman Officer Doug Morse.

That inquiry is in addition to a criminal investigation of Lisa Serna-Mayorga, a former mayoral staffer who resigned in July after it was revealed that she had allegedly used her city credit card for personal purchases. Sources have told The Bee those purchases included a trip to Disneyland and groceries.

Hart's credit card use was called into question during a recent examination of the credit card accounts for members of the City Council, the mayor and staff members in those offices.

"We did come up with two people and we're just looking at those people to see if there was any criminal wrongdoing," Morse said, referring to Hart and Serna-Mayorga.

Morse said the examination of the City Council and mayor offices found "nothing criminal in nature except for those two." He would not say what purchases by Hart were questionable.

The city Thursday released hundreds of transactions by the City Council and mayoral offices in response to a Public Records Act request submitted by The Bee. Transactions made by Hart and Serna-Mayorga were not included in the records released by the city.

City Manager John Shirey said the credit card records for Hart and Serna-Mayorga will be passed to the office of the Sacramento County district attorney.

Hart did not return a phone message seeking comment.

As the chief service officer, Hart worked with the mayor's office to increase volunteerism in the city. Hart's job was funded by a $200,000 grant from the Rockefeller Foundation, and he left the position earlier this year after the grant expired.

City spokeswoman Amy Williams said the city would not say who approved Hart's credit card purchases until the criminal investigations are complete.

Meanwhile, a separate, internal city audit released Thursday – which included only employees outside the mayor and council offices – found that while there were no "extensive personal purchases" made by city employees on credit cards, "some charges violated policy and lacked complete support."

The charges that violated policy included an unnamed department head who charged $89.60 for a hotel room upgrade at a conference and $593 for an employee to attend a conference in Arizona – after the City Council had voted in 2010 to boycott conducting business with that state following its passage of a strict immigration law.

The audit also found incomplete oversight by department heads.

While some charges apparently violated city policy, the purchases made by Hart and Serna-Mayorga are the only transactions that caught the eye of the Police Department.

"I'm relieved that after all of this review, that we didn't find any additional criminal wrongdoing or suspected criminal wrongdoing," Shirey said. "I'm not happy that this issue is front and center. We should have been more prudent and all I can say is we will bring it under control."

Between 2008 and July of this year, city employees – including those who work in the offices of the mayor and City Council – charged roughly $10 million to their credit cards, according to records released by the city. Shirey said he wants to scale back the number of credit cards issued to city employees.

All together, members of the City Council and mayoral staffers made $406,945 in charges between July 2007 and July 2012, records released Thursday show. Johnson does not use a city- issued credit card.

The mayor, in North Carolina campaigning for President Barack Obama on Thursday, was unavailable for comment. His spokesman, Joaquin McPeek, said, "We fully support the Sacramento Police Department's continued investigation of this issue. If there is any wrongdoing found, we support whatever actions will be taken to correct the situation."

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by Ryan Lillis

Order Reprint