People are offered free reusable bags as they enter the new Amazon Go store at Amazon's Seattle headquarters in Seattle, Washington, U.S., January 29, 2018. REUTERS/Lindsey Wasson

(Reuters) - Amazon.com Inc AMZN.O is bringing its grocery store without checkout lines to Chicago and San Francisco, the company said in a statement this week, confirming reports it will expand the concept beyond its pilot in Seattle.

Known as Amazon Go, the store is fashioned after small grocery shops with a crucial difference: it has no cashiers. Customers scan a smartphone app to enter the store, and then cameras and sensors track what they remove from the shelves and what they put back. Amazon then bills shoppers’ credit cards on file after they leave.

It was not clear when the new stores will open. Amazon posted job listings for Amazon Go store managers in San Francisco and Chicago last month. News of the listings was reported by The Seattle Times on Monday.

The concept has the potential to alter brick-and-mortar retail and has spawned similar designs from startups hoping to sell the technology to other retailers.