Zappos, one of the subsidiaries of Amazon, is believed to have exposed the names, email addresses, addresses, phone numbers, and password hashes of its customers in the breach that took place Sunday. The company however, maintains that credit card data was not exposed, though the hackers might have had access to the last four digits of customer credit cards.

Zappos also maintains that accounts or passwords maintained with the parent firm Amazon.com are not affected by the problem. Soon after the breach was noticed, company’s CEO, Tony Hsieh put up an explanation for the breach on the website, while at the same time blocking non-US traffic to the site.

Hsieh said hackers “gained access to parts of our internal network and systems” through one of the firm’s servers in Kentucky, The New York Times reports. Zappos has reset passwords and is in the process of notifying customers about the breach. In the aftermath of the data spillage, Zappos has suspended its telephone support operation, asking customers to contact it only via email.