Target said a massive payment card data breach that occurred during the first three weeks of the holiday shopping season affected up to 70 million people, far more than previously estimated.

Target’s shares were down 1.5 per cent at $62.40 before the bell today.

The company also cut its fourth-quarter adjusted earnings per share forecast for its US operations to $1.20 to $1.30, from $1.50 to $1.60.

Target said an ongoing forensic investigation showed that certain customer information in addition to payment card data was stolen during the data breach.

The investigation showed that the stolen information included names, mailing addresses, phone numbers and email addresses.

"I know that it is frustrating for our guests to learn that this information was taken and we are truly sorry they are having to endure this," chief executive Gregg Steinhafel said in a statement.

The Minneapolis-based company also forecast a 2.5 per cent decline in fourth-quarter same-store sales. It had previously sales to remain flat.

Reuters