Hours after the Secret Service confirmed that it is investigating a massive credit card security breach at Target stores that may have affected 40 million cards, the company has said that the thieves did not access PIN numbers.

As previously reported, the security breach was first reported by Brian Kreb on his blog. Kreb confirmed that the breach began on Black Friday, the day after Thanksgiving and the busiest shopping day of the year, and continued to Dec. 15. It likely affected all of the company’s nearly 1,800 stores in the U.S.

The Secret Service did confirm that it is investigating and Target later said that it is cooperating with the agency, which monitors the U.S.’ financial systems.

According to USA Today, Target has also confirmed that thieves gained access to customers’ names, credit/debit numbers, expiration date and the important three-digit CVV number on the back of the cards.

However, Target spokesman Eric Hausman said that there was “no indication” that PIN numbers for debit cards were acquired by the thieves. Another spokesperson told CNN that the issue that allowed the breach to happen in the first place was already fixed.

"Target's first priority is preserving the trust of our guests and we have moved swiftly to address this issue, so guests can shop with confidence," CEO Gregg Steinhafel said. "We regret any inconvenience this may cause."

Target has told customers to keep a close eye on their credit card statements. Meanwhile, American Express and Discover said they are “aware” of what happened.

image: Wikimedia Commons