The Amazon Go concept may be getting ready to go bigger.

Amazon is said to be testing even larger-format cashierless stores at a location in Seattle that’s set up to look like a more traditional grocery store — think of the Whole Foods layout, for example.

Quoting sources, The Wall Street Journal reports Amazon is experimenting with adapting its technology that tracks what shoppers grab from store shelves and then checks them out automatically as they leave, but seeing if it can work for bigger spaces with a lot more products and higher ceilings.

The Journal reports it is not clear if Amazon-owned Whole Foods is where the tech would be rolled out. “Amazon has previously said it has no plans to add the technology to Whole Foods,” the Journal writes, adding that both Amazon and Whole Foods have declined to comment on its report.

Amazon now has more than a half-dozen Amazon Go stores open or set to open in three cities — Seattle, Chicago and San Francisco — but they are much smaller than traditional grocery stores. In late September it was reported that Amazon is considering opening up to 3,000 Amazon Go locations by 2021.

Each Amazon Go store features a mix of grab-and-go breakfast, lunch and dinner options such as salads and sandwiches. Prominent are Amazon Meal Kits, items from local producers and some grocery essentials. Amazon Go stores tend to be between 1,200 and 2,300 square feet in size.

But larger- or different-format stores are also in Amazon’s playbook, even if they aren’t cashierless at this time. Beyond Whole Foods, Amazon has Amazon Books bookstores and newer Amazon 4-star stores for top-rated items.

The cashierless concept has not gone unnoticed by Amazon’s competitors. Walmart unveiled its Sam’s Club Now concept for Dallas in October, announcing it would take much of the Amazon Go approach and apply it to a larger, 32,000 square foot space.