NEW YORK - Wendy's (WEN) said hackers were able to steal customer's credit and debit card information at 1,025 of its U.S. restaurants, far more than it originally thought.

The hamburger chain said Thursday hackers were able to obtain card numbers, names, expiration dates and codes on the card, beginning in late fall. Some customer's cards were used to make fraudulent purchases at other stores. Wendy's urged customers to check their accounts for any fraudulent purchases.

The Dublin, Ohio, company first announced it was investigating a possible hack in January. In May, it said malware was found in fewer than 300 restaurants. About a month later, it said two types of malware were found, and the number of restaurants affected was "considerably higher."

Get Breaking News Delivered to Your Inbox

Wendy's has more than 5,700 restaurants in the U.S.

The company said Thursday it would post a list of affected restaurants on its website. As of Thursday afternoon, the list wasn't posted because of "technical difficulties."

In late afternoon trading, the stock is off 2.6 percent, or 25 cents, to $9.38.