ANNAPOLIS, Md. (AP) — A Maryland commission did not adequately investigate the impact of hospital overbilling identified through annual reviews, a state audit released Friday found, noting overcharges of at least $13.2 million at four hospitals.

The Office of Legislative Audits found that the Health Services Cost Review Commission did not determine how long overcharges had been occurring. The commission also did not discover the extent of prior year overcharges or the patients or payers that may have been overcharged, according to the audit.