Hundreds of federal health workers early on Tuesday learned their jobs had been cut, with many turned away at their office building doors, as the Department of Health and Human Services (HHS) moved forward with its mass restructuring plan.

The layoffs included several top officials and affected agencies responsible for overseeing the nation's food and drug safety, as well as those fighting disease.

Health Secretary Robert F Kennedy Jr announced last week that 10,000 workers would be laid off, and through voluntary departures, the workforce would be reduced from 80,000 to 60,000.

President Donald Trump has worked since inauguration day with adviser Elon Musk to slash the federal payroll.

The White House said last week that it planned to cut 3,500 full-time employees at the Food and Drug Administration (FDA) and 2,400 workers from the US Centers for Disease Control and Prevention (CDC). The administration has said it is cutting 1,200 employees from the National Institutes of Health, as well.

Health workers began hearing as early as 05:00 EDT (10:00 BST) on Tuesday that they were being dismissed.

Well before sunrise, Preston Burt, a communications specialist with the CDC's Division of Environmental Health Science and Practice for 10 years, received an email saying that he, along with his entire division, was laid off.

The division had hundreds of employees who worked with 33 states, primarily helping local health departments gather environmental health data and providing the public with information about hazards such as mercury and radon poisoning.

Two weeks ago, Burt and other division staff took part in an exercise to evaluate how to respond to a nuclear or radiological incident. All those staff members have been let go, he said.

"Now if there's a nuclear disaster, who are they going to call on as experts?" he asked.

While Burt was not shocked by the firing, others learned they had been laid off when they showed up to their offices and were unable to scan their badges to enter.

Employees waited in long lines outside to access the buildings during the confusion and chaos.

HHS is a department with a $1.8 trillion (£1.39 trillion) budget that oversees 13 agencies, including the CDC, the FDA and the Centers for Medicare & Medicaid Services.

The top officials laid off in the restructuring included the director of the National Institute of Allergy and Infectious Diseases, Jeanne Marrazzo. She succeeded Anthony Fauci in directing the agency that had led the US fight against Covid-19.

Marrazzo - and several other directors - were notified that they were being reassigned to HHS's Indian Health Service division in other locations, according to media reports. They were asked to decide by Wednesday whether they planned to accept the new roles.

The administration also fired FDA staff who were involved in the government's response to bird flu, according to Reuters. Outbreaks of the avian flu have caused egg prices to skyrocket, while cases in cows and humans have sparked concern among public health officials.

The cuts also come as the US is battling one of the worst measles outbreaks in a decade.

In a post on X, former Speaker Nancy Pelosi, who is still one of the more powerful members of the House of Representatives, said the administration's plans would "directly harm our most vulnerable communities and make America sicker".

"I will work with my colleagues in Congress to fight back against these shortsighted and irresponsible cuts," she said.

As a part of Kennedy's broader restructuring, HHS is also consolidating its 28 agency divisions into 15 new ones, including a new Administration for a Healthy America, to help carry out Kennedy's Make America Healthy Again agenda.

In announcing the changes, Kennedy said HHS was "inefficient as a whole" and that the cuts would remove "bureaucratic sprawl".

In a statement, HHS has said the cuts will save taxpayers an estimated $1.8b per year.

HHS has made cuts to public health funding, too. Last month, the administration announced it was pulling back $11b in Covid-19-era funding that states and local health departments were using for other purposes, including mental health and addiction as well as infectious disease outbreaks like measles and bird flu.

Washington, DC, and 23 states on Tuesday sued the US government for slashing the funding.

Republican Bill Cassidy, of Louisiana, and Independent Bernie Sanders, of Vermont, who lead the senate Health, Education, Labor, and Pensions committee have requested Kennedy to testify at a 10 April hearing to explain his "proposed reorganization" of HHS.