Munchery was a San Francisco on-demand food-delivery business and supplied prepared food items to San Francisco's Amazon Go stores. Employees at one Amazon Go location in San Francisco said it was not yet clear what would replace the Munchery items, but it would likely be another local supplier.

Shoppers at Amazon 's cashier-less convenience stores in San Francisco faced some empty shelves Tuesday morning after one of its local suppliers, Munchery, suddenly went out of business on Monday .

In an email to customers on Monday, Munchery said "Munchery is closing its doors and ending operations effective immediately," and "any outstanding orders with Munchery will be canceled and refunded."

Munchery was one of many on-demand meal kit companies that wanted to do it all: prepare meals and handle the delivery logistics for customers. Munchery raised $125.4 million in venture funding since it was founded in 2011, according to Crunchbase. Better-funded competitors like Blue Apron have also been struggling — Blue Apron priced its shares at $10/share when it went public in 2017, and it's now trading below $2. Ironically, Amazon's own movement into groceries with its 2017 acquisition of Whole Foods has put competitive pressure on these companies.

Amazon prepares some of its own food items for its Go stores, and gets some from local vendors. San Francisco Indian restaurant chain Dosa is another supplier for San Francisco Go stores.

Tuesday marked one year since Amazon opened its first cashier-less Go store to the public in Seattle. Since then they've opened eight more stores --three more in Seattle, two in San Francisco and three in Chicago. Amazon has plans for another in Chicago and has confirmed plans to open in New York City.

An Amazon spokesperson said, "Our Amazon Go stores feature a combination of ready-to-eat food items made by both our kitchen team and local kitchens and bakeries. We're excited to offer a range of local vendor favorites in our stores, such as...Dosa, La Boulangerie, Urban Remedy and more in San Francisco, and consistently evolve our overall selection to adjust to both customer feedback and incorporate new offerings."

WATCH: Amazon's cashier-less storefront continues to grow after one year in business