But company says it is "confident that PIN numbers are safe and secure."
Target said data connected to about 40 million credit and debit card accounts were stolen between Nov. 27 and Dec. 15. More than a dozen Target customers have filed federal lawsuits around the country, with some accusing Target of negligence in failing to protect customer data.
Target says the company is investigating, but it has not disclosed exactly how the breach occurred. Customers who see suspicious charges on their statements were advised to report them to their credit card companies and call Target at (866) 852-8680.
The Associated Press contributed to this report.