CNN has fired three employees who were coming into work at the media company without being vaccinated against COVID-19.

CNN media critic Oliver Darcy revealed a memo on Thursday from CNN Chief Jeff Zucker, which read, in part: "In the past week, we have been made aware of three employees who were coming to the office unvaccinated. All three have been terminated. Let me be clear -- we have a zero-tolerance policy on this."

There were no other details about what jobs the three employees held.

Darcy also said Zucker had postponed CNN's plan to have employees return in full to its offices by Sept. 7 and is now targeting mid-October.

"I think it is fair to say that we are all feeling a mix of anticipation, anxiety, frustration, confusion and exasperation -- I get it." Zucker's memo read, according to Darcy. "Continue to take care of yourselves and each other. And I will share more updates just as soon as we have them."

Up to now, CNN has been mandating vaccinations to return to its offices, but whether an employee was actually vaccinated was left up to the honor system. Zucker said that might change now and that masks would be required at CNN offices in Atlanta, Washington D.C., and Los Angeles.

The surge in COVID-19 cases, fueled by the Delta variant, is also creating challenges for other media companies.

The Associated Press announced Thursday that it had delayed its original Sept. 13 return-to-office plan. And Fox News announced last month that it required masks and social distancing for those employees who do not show proof of vaccination./aa