(CNN) The number of Transportation Security Administration employees taking unscheduled absences has increased steadily since the shutdown started and since CNN first reported on the phenomenon. In the last week, it was at times more than twice what it was at the same time last year, according to data released by TSA.

Some travelers are seeing the effects, with some airports experiencing much longer wait times to pass through security. Other airports have had to cut back their operations. Miami International Airport closed a concourse for several days due to a shortage of TSA screeners. In Houston, part of one terminal closed

Security experts are also noticing. They say that if these staffing issues persist , the mix of understaffing and higher workload could lead to airport safety becoming a serious concern. However, they say that point is still a way off.

But after the new year, the absence rate shot up. The TSA's unscheduled absence rate was generally around 3% after the first week of January last year. This year, it's hovered between 5 and 7%. The trend of unscheduled absences has increased markedly as the shutdown, which began Dec. 22, has ground on. In 2017, absences increased slightly over the holidays, as they did in 2018, too.But after the new year, the absence rate shot up. The TSA's unscheduled absence rate was generally around 3% after the first week of January last year. This year, it's hovered between 5 and 7%. CNN first reported on the uptick in unscheduled absences on Jan. 4.

The TSA is upfront about why workers are calling out: "many employees are reporting that they are not able to report to work due to financial limitations," the agency said in a release

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