An accounts payable audit conducted by a former Department of Justice financial crimes auditor revealed that the Sacramento, California, library had made numerous overpayments for maintenance projects between 2004 and 2007, according to the Sacramento Bee.

The auditor, Edward Hudson, found two maintenance firms that carried out work for the library passed along just $562,500 of the more than $1.3 million they received to contractors.

"I don't see where the library got value for what they were being charged," Hudson told a Sacramento Superior Court jury, as quoted by the news source. He noted that typically, companies generate approximately 7 to 10 percent profit margins.

The two firms are headed by the same person, Janie Rankins-Mayle, who has been charged with two counts of grand theft and one count of bribery.

Additionally, Hudson uncovered other improper charges, including expenses related to "Direct TV, Chinese food, a Mercedes-Benz dealership and (Oregon condominium complex) Gold Beach Resort," the media outlet reports.

It's important to conduct regular AP audits as these can help identify overpayments, duplicate payments and other irregularities.