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More than two dozen Federal Emergency Management Agency employees, including at least one who worked in the agency's main response center, have tested positive for the coronavirus, sources told NBC News on Tuesday.

People are "dropping like flies" — in terms of being temporarily sidelined by COVID-19, the disease associated with the coronavirus — said a person familiar with the response effort who spoke on the condition of anonymity because the person was not authorized to speak on the record.

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This week, some people who work in the National Response Coordinating Center, the nerve center of disaster response for the lead agency in this emergency and others, have been sent into quarantine because at least one person who worked in the space tested positive, according to that person and another source familiar with the situation.

The response center is cleaned regularly so it can continue to be used regardless of positive tests.

A FEMA spokesperson would not say how many people who work in the response center have tested positive but confirmed in an email that as of Tuesday, April 14, "there were 25 FEMA employees who tested positive for COVID-19."

The overall number of people working at FEMA headquarters who have tested positive could be different because other agencies and private-sector companies have employees engaged in the coronavirus response at the agency's Washington offices. Last week, NBC News reported that members of a key supply-chain task force were told to work remotely because someone who worked in other areas of the headquarters had tested positive.

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"The health and safety of the workforce, including our interagency partners and members of the White House Coronavirus Task force, is a top priority for the Federal Emergency Management Agency as we continue to lead the federal operations in response to the pandemic," the FEMA spokesperson said. "Like many large employers, FEMA has employees who have tested positive."

Three people familiar with the response effort said protective practices like wearing masks and gloves remain optional during the crisis, which has pared the workforce at the agency to only the most essential employees.

The FEMA spokesperson declined to address the specifics of protective gear policy in the national response center but said the agency is taking "every precaution recommended by the CDC to protect all employees."