The discount retailer says a security breach during the holiday shopping season is wider and deeper than first thought.

It now says up to 70 million customers may have been impacted by data theft, compared to an earlier forecast of 40 million.

Target did not reveal whether data were stolen in store, from its website, or a combination of both.

It apologized once again and reassured customers that unexpected charges will be covered.

Security experts warn this breach could end up being the biggest ever in retail history.