OKLAHOMA CITY — Sonic Drive-In is the latest company to be affected by a credit card security breach.

The website KrebsOnSecurity.com reported the breach involved the theft of 5 million credit and debit card numbers used at Sonic's 3,600 locations nationwide, numbers that were then sold on the black market to be used fraudulently.

In a statement, Sonic told the website that its credit card processor detected "unusual activity" involving cards used at Sonic. The chain is working with third-party forensic experts and law enforcement to investigate the breach further.

The company has not issued a statement about the breach on its website or social media as of Wednesday morning.

Sonic has 17 locations throughout New Jersey.

Fellow chain Chipotle suffered a breach last spring with "irregular credit card transactions."

Earlier this month, credit monitoring company Equifax announced a high-tech breach that exposed Social Security numbers and other sensitive information about 143 million Americans.

Contact reporter Dan Alexander at dan.alexander@townsquaremedia.com.

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