One of the largest home remodeling companies is investigating the possibility that they were hacked.

Home Depot said: "I can confirm that we’re looking into some unusual activity and we are working with our banking partners and law enforcement to investigate."

"Protecting our customers' information is something we take extremely seriously, and we are aggressively gathering facts at this point while working to protect customers. If we confirm that a breach has occurred, we will make sure customers are notified immediately. Right now, for security reasons, it would be inappropriate for us to speculate further. We will provide further information as soon as possible."

Multiple banks have reported that a large number of stolen credit and debit cards have appeared for sale online that appear to have come from Home Depot, according to security blogger Brian Krebs. Banking contacts told Krebs that the financial data appeared to have been stolen between late April and early May 2014.

Given the number of Home Depot stores, this could be the largest retail hack in history.