WASHINGTON — A medical professional who conducted passenger screenings at Los Angeles International Airport tested positive for the coronavirus late Tuesday , according to the Department of Homeland Security and an internal email obtained by NBC News.

The person last worked screening air travelers for illness on Feb. 21, DHS said in a statement released Wednesday, which also said the medical professional had worn the proper protective gear while working. The internal email described the person as a "contract medical screener" for the Centers for Disease Control and Prevention.

The email also said "these screeners are predominantly assigned to the CDC in-transit lounge and a few support jetway screening on direct flights from China."

In its statement, DHS said: "Late last night, DHS headquarters was alerted to a situation where one of our contracted medical professionals conducting screenings at LAX international airport had tested positive for COVID-19, also known as the coronavirus. This individual is currently under self-quarantine at home with mild symptoms and under medical supervision. Their immediate family is also under home quarantine."

According to DHS, the person began to exhibit cold-like symptoms Saturday and visited a primary care doctor Sunday. The person was tested for COVID-19, which came back positive Tuesday.

The person's last shift at LAX was Feb. 21, more than a week before the appearance of symptoms. According to the internal email, the screener worked at LAX from Feb. 14 to 21 and became symptomatic on Feb. 29.

"DHS is happy to report that this individual was highly trained and did everything right both on the job and when they began to feel sick," DHS said. "We are told the individual wore all the correct protective equipment and took necessary protections on the job. Additionally, as soon as the individual began to feel sick, they self-quarantined, saw a physician, and reported to the appropriate authorities and officials."

Acting Commissioner of Customs and Border Protection Mark Morgan said Thursday that he was "confident we are taking the appropriate steps in response to that incident, to include contact tracing."

DHS said it is working to communicate with the person's co-workers and to trace contacts.

"At this time we do not know if this case is a result from community spread or through their work as a medical screener," DHS said. "There have been no positive COVID-19 detections reported from the LAX screened travelers. This is an evolving situation that the CDC, DHS and county public health officials continue to examine."

The internal email said the "CDC contracted screener was an augmented screener secured" by the Countering Weapons of Mass Destruction Office, or CWMD, which is part of DHS.

Acting Deputy Homeland Security Secretary Ken Cuccinelli said at a White House briefing by the President's Coronavirus Task Force on Jan. 31 that "our chief medical officer in the department is in CWMD, and [we] were providing medical support at the airports."

"We're using contract authority that we have to backfill the CDC personnel, so they can be freed up for other missions at the airports where medical screening is being focused," Cuccinelli said.

At a news conference Wednesday, Los Angeles Mayor Eric Garcetti said: "I want to go out of my way to thank our federal officials we have been working with. [They] have really worked to make sure that ships that are coming into the port are screened, the passengers that are coming into LAX are being screened — the fourth-busiest airport in the world and the busiest container terminal in the Americas."

Laura Strickler reported from Washington. Andrew Blankstein reported from Los Angeles.