(NewsNation) — The nation’s largest grocery store chain is under scrutiny for its use of electronic price tags, raising concerns that prices could be adjusted on a whim.

Democratic Sens. Elizabeth Warren of Massachusetts and Bob Casey of Pennsylvania, both facing reelection soon, recently sent a letter to Kroger questioning their practices. They’re concerned the grocery chain might be using technology, known as electronic shelving labels, to raise prices when shopping is at its busiest.

This could potentially anger consumers, although some may have seen it at stores like Best Buy, Amazon Fresh and Walmart.

Kroger uses digital labels at 500 stores

Senators are concerned that companies, specifically Kroger and its many subsidiaries like Ralphs, Fred Meyers and King Soopers, may be exploiting shoppers.

The grocery giant started using these “digital labels” at a few dozen stores in 2018 and expanded it to 500 last year, claiming the technology saves employees time and allows them to be more productive.

In their letter to Kroger’s CEO, Warren and Casey wrote that “widespread adoption of digital price tags appears poised to enable large grocery store to squeeze consumers to increase profits.”

They cite analysts’ predictions that so-called dynamic pricing could result in grocery bills being adjusted like airline tickets.

How has Kroger responded?

NewsNation contacted Kroger, which said its stores are dedicated to constantly lowering prices.

“Everything we do is designed to support this strategy, and customers are shopping more with Kroger now than ever because we are fighting inflation and providing great value. Any test of electronic shelf tags is to lower prices more for customers where it matters most. To suggest otherwise is not true,” the company said.

Earlier this year, the Federal Trade Commission investigated allegations of price gouging at Kroger but didn’t find any definitive proof.

Kroger is allowed to adjust its process as long as it doesn’t conspire with suppliers.