Amazon.com Inc said today it was searching for a location to build its second headquarters in North America that would cost more than $5 billion and house up to 50,000 staff.

The e-commerce company, which is headquartered in Seattle, said it was seeking proposals from local and state government leaders and would select the location next year.

Amazon's workforce has exploded to more than 380,000 from under 25,000 since it moved to Seattle in 2010, as it rapidly expanded to become a global retailer - selling everything from groceries to appliances.

The new headquarters should ideally be located in a metropolitan area with more than one million people, potentially giving the company a shopping list of more than 50 cities to choose from

The company's total revenue has grown to $136 billion at the end of last year from $34 billion in 2010. Amazon recently snatched up Whole Foods Market for $13.7 billion.

Amazon said the new headquarters should ideally be located in a metropolitan area with more than one million people, potentially giving the company a shopping list of more than 50 cities to choose from.

"We want to find a city that is excited to work with us and where our customers, employees, and the community can all benefit," Amazon said.

Amazon is looking for a favourable tax structure and local government subsidies, incentives that have attracted other companies like Taiwan-based Foxconn to build a $10 billion liquid crystal display factory in Wisconsin. The state's Republican-controlled government had voted to approve a bill aimed at establishing a $3 billion incentive package for the plant.

Amazon expects the new headquarters to be a "full equal" to its Seattle office, chief executive Jeff Bezos said in a statement.

The Seattle campus is spread across 33 buildings and employs more than 40,000 people.