The facilities that make up Amazon's vast logistics network vary in size and headcount depending on their function. Some fulfillment centers are the size of 26 football fields and employ thousands of workers, making it challenging for Amazon to ensure social distancing rules.

Amazon has ordered workers at warehouses across the country to stay 6 feet away from their colleagues, among other protective measures, in order to limit the spread of the coronavirus.

The company began notifying warehouse workers in recent days that if they fail to follow social distancing rules, they could face disciplinary action, according to a document obtained by CNBC. The first violation will result in a written warning, and if employees are caught a second time, they could get fired.

An Amazon spokesperson confirmed to CNBC that employees who "intentionally violate" social distancing rules will be given two warnings and on the second documented offense, "termination could occur." The spokesperson said the policy applies to all warehouse employees at its facilities.

"We've had some instances of employees intentionally violating our clear guidelines on social distancing at our sites, which endangers both the individual and their colleagues," the spokesperson said. "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."

It's unclear how Amazon is identifying employees who have violated the rules. In a blog post published last week, Dave Clark, who runs Amazon's retail operations, said the company would use its "top machine learning technologists" to detect areas where it can improve social distancing in its facilities by relying on internal camera systems.

Three Amazon warehouse workers who asked to remain anonymous said they were told by site leadership that their facilities would identify individuals as they see them violate the rules, as well as by reviewing camera footage. The workers also expressed concerns that the policy would be unfairly applied to floor associates and not site leadership.

One worker at a facility in Michigan said they noticed several managers who appeared to be flouting the rules by "huddling around the time clock." They added that they're aware of several associates at their facility who have been warned for not following social distancing rules.

A worker at a facility in Illinois said they appreciated Amazon's efforts to make sure employees are following social distancing rules. They said their facility has put tape down on the floor to advise workers on where they can stand safely, as well as reconfigured the cafeterias so that workers don't sit next to each other, among other steps.

"It was very hard to get into people's heads that they need to abide by this," the worker said. "People really weren't paying a lot of attention. But we don't want anybody to do anything that's unsafe."

In addition to social distancing rules, Amazon said it has instituted temperature checks at its facilities. It has also supplied workers with face masks and taken steps to increase cleaning at its facilities by providing workers with sanitizer and disinfectant wipes, the company said.

Still, Amazon employees who spoke to CNBC argue that these efforts aren't enough to keep them safe. Last week, workers at Amazon facilities in New York and Michigan staged protests to demand the company shut down their warehouses after they reported confirmed coronavirus cases there.

A worker at a facility in Indiana said they felt it was unfair of Amazon to take disciplinary action against employees who violate social distancing rules. Instead, they said Amazon should be helping employees get tested for the virus.

"We do not feel safe in our building anymore. I'm frustrated with it," the worker said. "If they're having to go to all these great lengths to keep us safe, I feel like they need to shut down the building for two weeks so they can actually get cleaned."