Shares of the Seattle internet retail giant were off slightly to $1,744.99.
Amazon is testing a supermarket equipped with Go technology in a 10,400-square-foot space in Seattle's Capitol Hill neighborhood, a person familiar with the project told Bloomberg.
The company, which already operates the Whole Foods Market chain, last week confirmed plans to launch a separate supermarket brand, starting with a location in the Woodland Hills neighborhood of Los Angeles.
These stores will have human cashiers, while Go revives Amazon's original vision of creating full-size grocery stores without checkout lines.
Amazon opened the first Go convenience store at its Seattle headquarters almost two years ago and now operates 21 locations around the U.S.
A user of the tech downloads the Amazon app, browses the store, takes what he or she wants and leaves. The system tracks what customers take from and return to the shelves and bills their Amazon accounts for their purchases.
While customers have praised the Go stores as technical marvels, Bloomberg noted that retail analysts have wondered whether the low margins at a typical corner-store chain would offset the costs of the Go technology.
The tech includes cameras and software that determine what shoppers have grabbed and automatically charges them when they exit.
Newer versions of Go's hardware are said to feature fewer backroom servers and more efficient cameras, software and networking capabilities, substantially reducing the cost of setting up a new store.
Most Go locations are close to 2,000 square feet and stock grab-and-go staples -- cold drinks, packaged sandwiches, salads -- and a smaller selection of household items like cold medicine and phone chargers.
Bloomberg said the newer technology will bring Amazon closer to its original goal of a larger supermarket.