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Amazon is threatening to fire warehouse workers repeatedly caught breaking social-distancing rules aimed at limiting the spread of the coronavirus.

The e-commerce behemoth says warehouse staffers will get a warning for their first violation of the guidelines, which instruct workers to stay six feet apart from each other — but a second offense could get them canned.

“We are taking intense measures to ensure the health and safety of employees across our sites who are performing an essential role for their communities during this crisis,” Amazon spokesperson Rachael Lighty said in a statement.

The crackdown follows vocal criticism of how the Seattle-based company has handled concerns about the virus while responding to a massive surge in demand for its products as the pandemic shuts consumers in their homes. CNBC first reported on the disciplinary measures Monday.

It’s unclear exactly how Amazon will enforce the social-distancing rules, but three warehouse workers told CNBC that officials plan to single out staffers who are seen breaking them and review camera footage to spot violations.

An Amazon executive said last week that the company has asked some of its “top machine learning technologists” to find ways to improve social distancing in its buildings by using internal cameras.

“With over 1,000 sites around the world, and so many measures and precautions rapidly rolled out over the past several weeks, there may be instances where we don’t get it perfect, but I can assure you that’s just what they’ll be — exceptions,” Dave Clark, Amazon’s senior vice president of worldwide operations, said in a Thursday blog post.

Workers have called on Amazon to close warehouses until there’s a comprehensive plan in place to protect staff from the virus. They have also complained that the company has failed to provide protective gear such as masks and gloves, though Amazon said masks would be available at all locations as soon as Tuesday.

Workers staged their second strike in a week Monday at Amazon’s Staten Island fulfillment center, where staff have reported more than two dozen coronavirus cases. Amazon sparked outrage last week when it fired Chris Smalls, the management assistant who organized the March 30 walkout on Staten Island.