United Natural Foods Inc and Oak Street Real Estate Capital are separately working on bids for U.S. food distributor SpartanNash Co, people familiar the matter said on Tuesday.

United Natural Foods, a SpartanNash competitor, is exploring a bid to buy the entire company, the sources said.

Oak Street, a Chicago-based investment firm, contacted SpartanNash last month to reiterate its interest in buying real estate from the company worth up to $1 billion, shortly after two activist investors began pushing SpartanNash to explore changes, including putting itself up for sale, the sources added.

There is no certainty of a deal, said the sources, who asked not to be identified in order to discuss the private conversations.

Representatives for SpartanNash and United Natural Foods did not respond to requests for comment while Oak Street declined to comment.

SpartanNash, which is based in Byron Center, Michigan and has a market value of $1.3 billion, owns 145 supermarkets, primarily under the banners of Family Fare, Martin's Super Markets and D&W Fresh Market and operates commissaries for the U.S. military.

Last month, activist investors Macellum Advisors and Ancora Holdings Group, which previously teamed up to push for changes at retailer Kohl's Corp nominated three candidates to SpartanNash's board. The investors, ho own roughly 4.5% of the company's stock, are pushing for the board to consider a full or partial sale.

Representatives for the two hedge funds declined to comment.

SpartanNash refreshed its board earlier this year after appointing Tony Sarsam as its CEO in 2020. Its stock price has climbed 33% this year but it is down 8% over the past five years.

Four years ago, United Natural Foods purchased SUPERVALU for $2.9 billion and used the acquisition to expand its grocery distribution network. United Natural Foods is valued at $2.7 billion and its stock price has climbed nearly 30% in the last 52 weeks.