Target says the Justice Department will be investigating its recent security breach.
The retail giant made public last week that credit and debit card data from around 40 million shoppers may have been compromised.
It's the second largest credit card hack in U.S. history.
People who shopped between November 27 and December 15 may be affected.
Target also has an internal investigation under way, which it says the Secret Service is helping with.
The company has offered free credit-monitoring services to those affected by the hack.
So far, customers have filed more than a dozen lawsuits.