The state Department of Insurance is investigating alleged fraud against Aetna health plan members by the 1-800-GET-THIN Lap-Band surgery centers.
The Food and Drug Administration and the Los Angeles County Board of Supervisors are already investigating eight Southern California surgery centers over allegations they used misleading ads to promote the weight-loss surgery.
A Pasadena-based marketing firm is also under investigation.
An attorney representing the surgery centers says he has not been formally notified of any insurance investigation.
He added that no evidence of wrongdoing has ever been found at the facilities.
The Associated Press contributed to this report.