Employees of the Department of Health and Human Services wait outside the Mary E Switzer Memorial Building after it was reported that the Trump administration fired staff at the Centers for Disease Control and Prevention and at the Food and Drug Administration. Photo: Kevin Lamarque/ Reuters

The Trump administration fired staff at the Centers for Disease Control and Prevention and at the Food and Drug Administration on Tuesday, as it embarked on its plan to cut 10,000 jobs at the Department of Health and Human Services, according to two sources familiar with the situation.

The cuts are part of a wide plan by President Donald Trump and billionaire ally Elon Musk to shrink staffing levels in federal departments and agencies.

Health Secretary Robert F Kennedy Jr has described the cuts at the CDC and the FDA as essential to streamlining a bloated bureaucracy. However the cuts - including earlier dismissals - have led to the departures of top scientists at key agencies for public health, cancer research and drug oversight, raising concerns about how the US will safely oversee the health sector and respond to emergencies.

Brian King, head of the FDA's Center for Tobacco Products, was fired, according to an email sent by King to FDA staff seen by Reuters.

Peter Stein, the director of the Office of New Drugs in the FDA's Center for Drug Evaluation and Research division, resigned on Tuesday, according to one source familiar with the matter.

King and Stein's exits adds to top leadership departures across the FDA's divisions including drugs, food, vaccines, medical devices and tobacco products. Staff have also been leaving and some employees reviewing products say they are struggling to meet their deadlines.

An FDA employee said staff had to present their badges at the building entrance and those who had been fired were given a ticket and told to return home, according to one source.

At the CDC, fired staff worked at National Center for Environmental Health, Substance Abuse and Mental Health Services Administration, and National Center for Immunization and Respiratory Diseases, according to the second source.

The cuts at NCIRD included at least one person working on the federal response to measles outbreaks, the source said.

Officials at the US Department of Health and Human Services were not immediately available for comment.