OKLAHOMA CITY - Sonic has acknowledged possible security breach at its drive in restaurants.  That information from the online cyber security blog Krebs On Security.

The blog says Sonic, based in Oklahoma City, believes the breach has impacted a number of store payment systems.

The blog is reporting stolen credit and debit cards are now for sale online and at a higher price than normal because most of the card holders don't realize their cards are compromised, meaning the cards are all still active.

In a statement to the blog, Sonic says "Our credit card processor informed us last week of unusual activity regarding credit cards used at SONIC. We are working to understand the nature and scope of this issue, as we know how important this is to our guests.  We immediately engaged third-party forensic experts and law enforcement when we heard from our processor. While law enforcement limits the information we can share, we will communicate additional information as we are able."

Christi Woodworth, vice president of public relations at Sonic told Krebs On Security, the investigation is still in its early stages, and the company does not yet know how many or which of its stores may be impacted.

Sonic has more than 3,600 locations in 45 states across the U.S.