A Department of Homeland Security spokesman lashed out at CNN on Friday, labeling as "fake news" the network's report that hundreds of Transportation Security Administration screeners at the nation’s airports have been staging a "sick out" this week amid the partial government shutdown.

In a tweet, DHS spokesman Tyler Houlton accused the network of failing to validate its data and not reaching out to agency officials for verification.

"More #FakeNews from @CNN. Security operations at airports have not been impacted by a non-existent sick out. CNN has the cell numbers of multiple @TSA public affairs professionals, but rather than validate statistics, they grossly misrepresented them," the tweet read.

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In response to tweets by Houlton and President Donald Trump, CNN said it spoke with several TSA and union officials and used data provided by the employee unions.

"CNN spoke to numerous TSA & union officials & cited data provided by unions for our report. TSA itself put out a statement acknowledging increased call-outs after we published. @spoxdhs & @realdonaldtrump may not like the truth but that won’t stop us from reporting. #FactsFirst," the tweet read.

The TSA, meanwhile, tweeted a more measured response to the CNN report that said employee absences began over the holidays but have had minimal impact on security operations.

"Call outs began over the Holiday period and have increased, but are causing minimal impact given there are 51,739 employees supporting the screening process," the tweet said. "TSA is grateful to the agents who show up to work, remain focused on the mission and respectful to the traveling public."

Even in the middle of the shutdown, TSA officers are mandated to work without pay.

Employee union officials told the New York Times that TSA workers at several major airports have called in sick since the shutdown began Dec. 22. More than 150 called out Friday from Kennedy International Airport in New York City, according to the paper.

One unnamed federal official said the call-outs seemed to be part of a coordinated protest, but union officials said many employees who called out sick were most likely looking for alternative employment to make up for lost wages.

The shutdown is beginning its third week.

A TSA spokesperson told the Times that wait times for passengers to board flights could increase if the call-outs persist, and that the agency "is grateful to the agents who show up to work, remain focused on the mission and respectful to the traveling public as they continue the important work necessary to secure the nation’s transportation systems.”

The concern over airport security staffing followed speculation last month over whether Homeland Security Secretary Kirstjen Nielsen would keep her job.

TSA Administrator David Pekoske recently urged President Trump to keep Nielsen despite reports that the president had grown frustrated with her leadership.

"I've worked for Secretary Nielsen for a little over a year now and in my view, she’s been an outstanding secretary of homeland security," said Pekoske, according to the Washington Examiner. "And she has been very, very supportive of me as the TSA administrator, very interested in our issues, and importantly, very engaged with our workforce."