A third TSA agent at DFW International Airport has tested positive for COVID-19 as a growing number of security workers come down with the virus.

According to the Transportation Security Administration, the agent last worked Monday as a screening officer at the C21 checkpoint between 12:30 and 9 p.m. The agency said 56 TSA screening agents and 16 non-screening workers have now tested positive nationwide, including 15 at New York’s John F. Kennedy International Airport.

A handful of workers at DFW International Airport have been confirmed to have tested positive for COVID-19, including a baggage handler for American Airlines and a pilot for American.

Among the TSA agents, one of the screening agents last worked on March 25 from 4 to 7 a.m. at Terminal E at the Gate 18 security area. The other last worked March 22 from 4 a.m. to 6 a.m. in Terminal D at the Gate 18 checkpoint.

DFW is among the busiest airports in the country but has seen a severe drop in traffic since the COVID-19 pandemic ramped up in the United States in March. The TSA has now shut down seven of DFW’s 14 checkpoints. Dozens of shops and restaurants have also closed.

Airlines canceled nearly half of the flights scheduled for DFW Airport on Friday, according to FlightAware.

The TSA has not reported any positive COVID-19 cases among workers at Dallas Love Field. A screening agent at Houston’s George Bush Intercontinental Airport has tested positive and last worked Tuesday.

TSA is allowing screening agents to wear surgical masks, and they always wear nitrile gloves.