Los Angeles City Controller Wendy Greuel said Wednesday she is opening an investigation of the Department of Building and Safety's billing practices after her office uncovered dozens of cases in which customers were overcharged or possibly undercharged.

The incidents were uncovered during an audit of the department's management controls, ordered in the wake of a bribery scandal last year that rocked the department and resulted in the criminal convictions of two building inspectors.

As part of her review of the department's management practices, Greuel - who is running for mayor - found that it sometimes wrongly charged applicants permit fees for projects valued under $500 and also charged extra fees for projects that required multiple permits.

The department also might have undercharged for some permits by not reviewing construction cost estimates, which determine the price of permit fees, Greuel's audit found.