Visa has revealed that at least one state attorney general’s office is looking into several aspects of the company’s debit card practices.

In a note in its latest quarterly filing with the Securities and Exchange Commission [PDF], Visa disclosed that the office of Ohio Attorney General Mike DeWine recently made investigative demands of the company with regard to its debit card business.

Visa says DeWine’s office sought “documents and information focusing on Visa’s rules related to the acceptance of Visa debit cards, as well as cardholder verification methods and the routing of Visa debit transactions.”

While it’s unclear exactly what the Ohio AG is investigating, merchants have accused Visa — and, in some cases, MasterCard — of forcing them to use their verification networks for debit cards, instead of less-expensive verification services that confirm the cardholder via a PIN. The retailers also say that PIN verification is more secure than the pricier system they allege they are being strong-armed into using.

Walmart, Kroger, and Home Depot have each filed lawsuits against Visa over its debit card verification practices.

Visa says it is cooperating with the AG DeWine’s requests.

UPDATE: When reached for comment, the Ohio AG’s office could only confirm that the investigation involves chip-embedded debit cards (as opposed to older cards with just magnetic stripes).

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