Online footwear retailer Zappos.com is planning a major expansion of its Kentucky warehouse and distribution centre with at least 200 extra workers to be hired in the next two years.

The San Francisco-based company has already outgrown its 120,000-square-foot facility in Shepherdsville, Bullit County, and has begun moving ground for a 160,000-square-foot expansion according to company officials.

"We stayed small in the beginning, employee-wise, and now we're certainly seeing more success than we expected," operations manager Keith Glynn said.

The company currently employs 50 full-time staff.

Although Zappos operates two stores in California and a warehouse outlet in Shepherdsville, online retailing accounts for 99 per cent of the company's total sales, which have doubled each year since it began trading four years ago.

Last year, the company posted sales of $70 million and forecasts sales of $140m for 2004, with plans to expand into handbags and children's shoes.