ALBANY (AP)  New York’s attorney general, Andrew M. Cuomo, said Thursday that he had issued new subpoenas to Aetna, Cigna, the UnitedHealth Group, WellPoint and other health insurers in a broadening investigation of a practice that he said was unfairly costing consumers hundreds of millions of dollars.

He is also looking to subpoena testimony from the chief executives of those companies, as well as from executives of Empire Blue Cross Blue Shield, Excellus and the combined Group Health Inc. and HIP Health Plan.

Mr. Cuomo says he believes the companies used a company called Ingenix, which is owned by UnitedHealth, to set payment rates for medical treatments that resulted in consumers being reimbursed at unjustifiably low rates. Low reimbursements mean higher out-of-pocket costs for consumers when they choose or need doctors outside their health plans.

“Ingenix is a wholly owned subsidiary of the industry, and the company is determining the rates that the insurance companies use to reimburse consumers,” Mr. Cuomo said.