Zappos.com, the popular shoe website, was the victim of a cyber attack that exposed customer information on the company's internal network and systems, Chief Executive Tony Hsieh said in an email to employees.

In a separate email to account holders, the company said the potentially exposed information included names, email addresses, billing and shipping addresses, phone numbers and the last four digits of credit card numbers.

Zappos said the database that stores full credit card numbers and other payment data was not affected or accessed. Hsieh said the Henderson, Nev., company was cooperating with law enforcement in "an exhaustive investigation."

Zappos said it has more than 24 million customer accounts in its database. For the time being, the company will not be answering customer inquiries by phone.

Zappos, which sells shoes and has since expanded to other retail categories, was bought by Seattle-based Amazon.com Inc. in 2009 in a deal worth nearly $900 million.

Zappos has become known for its customer service, generous returns policy and for its quirky company culture led by Hsieh _ including head-shaving events, impromptu parades around the cubicles and employee birthday pranks, Los Angeles Times reported.