Walmart and Kroeger are hiking the prices of at-home COVID test kits after a deal with the White House to sell them for $14 expired. In September, the two retailers and Amazon agreed to sell two-pack rapid testing kits at a discounted price for three months.

Now that the deal has lapsed, the BinaxNOW kits are being sold at Walmart for $19.88 while Kroeger has them listed for $23.99, though they are sold out. Walmart has another brand of rapid test available for $29.99, while all the tests sold by Kroeger are out of stock.

There are at-home rapid antigen tests available on Amazon, with the cheapest listed at $17.99.

A Walmart spokesperson told NBC News that they kept the price lower throughout the holidays, even though the deal had expired. She said the retailer is working on getting more testing kits as quickly as possible.

The price hikes come as demand for testing kits has surged due to the highly transmissible Omicron variant. With at-home testing kits sold out in many places, people are being forced to wait in line for hours to get a PCR test. In addition, the large number of people getting tested has also caused a backlog at the labs processing the results, leaving people waiting several days to find out if they tested positive.