Amazon.com Inc.’s announced $13.7 billion acquisition of upscale grocery chain Whole Foods Market sent shock waves through the retail industry on Friday morning.

But at least one financial services firm says it’s not a done deal yet, and that another company could swoop in and acquire Whole Foods out from under Amazon, No. 1 in the 2017 Internet Retailer Top 500.

Analysts from Barclays write in a note that they “would not be surprised if there is a bidding war for WFM (Whole Foods),” citing Wal-Mart Stores Inc. (No. 3), Target Corp. (No. 20), and The Kroger Co. (No. 88) as retailers that might be interested in outbidding Amazon for Whole Foods. None of the three aforementioned retailers has publicly expressed interest in Whole Foods. An industry source says that Target has no interest in acquiring Whole Foods or submitting a bid. Kroger declined to comment. Wal-Mart did not immediately return a request for comment on any potential interest in acquiring Whole Foods.

“In theory, all retailers that sell food and compete with AMZN (Amazon) (could potentially enter a bidding war for Whole Foods) because we think most have too much to lose not to bid,” Barclays writes in its note. “AMZN has deep pockets, very few entities could outbid AMZN for WFM, but many will do anything to make this acquisition more costly for AMZN.”

Amazon says it expects its acquisition of Whole Foods to close in the second half of this year.

However, some are calling on the government to stymie Amazon’s acquisition of Whole Foods.

The Institute For Local Self-Reliance (ILSR), a nonprofit organization that advocates for small businesses, today called on antitrust regulators to block the deal, citing concerns about its impact on retail competition.

“Amazon’s acquisition of Whole Foods raises significant anti-competitive issues that should be deeply concerning to federal antitrust regulators and the public,” said ILSR co-director Stacy Mitchell. “This deal would allow Amazon to leverage Whole Foods’ 444 U.S. stores in ways that would dramatically amplify Amazon’s online market power by integrating these locations into its vast logistics and delivery network. It would give Amazon, which already sells more clothing, books, toys, and consumer electronics than any other retailer, a substantial share of an even bigger consumer goods category, groceries.”

An Amazon spokesman declined to comment on the Barclays note and the ILSR statement.