The Trump administration has fired staff who were working on the U.S. Food and Drug Administration's bird flu response as part of its mass layoffs at the Department of Health and Human Services, according to the American Veterinary Medical Association and a source familiar with the situation.

The Tuesday firings, which many employees learned of as they attempted to enter office buildings and were denied access, are part of the administration's effort to shrink the federal government.

Health Secretary Robert F. Kennedy Jr. has said he will fire 10,000 people across the agencies under the health department.

Among those fired were leadership and administrative staff at the FDA's Center for Veterinary Medicine, according to the source.

The FDA did not respond to a request for comment.

An employee at the Center for Veterinary Medicine said almost all the administrative staff were terminated, along with staff on the policy, legal and external communications teams.

Managers were also eliminated in the office of the center's director, said the employee, who recently took part in a deferred resignation program that reduced the government's headcount.

The American Veterinary Medical Association wants to work with the U.S. Congress and the administration to restore key positions eliminated within the health department, President Sandra Faeh said. Department cutbacks affected offices dealing with bird flu, animal and human food safety, and other issues, she said.

The FDA center's Veterinary Laboratory Investigation and Response Network tests pet food for bird flu. The FDA has issued raw pet food recalls after detecting bird flu contamination that was linked to the deaths of house cats.

The laboratory program office told staff in an email sent on Tuesday that job cuts at the center "may cause significant challenges and delays," according to a copy of the email seen by Reuters.

While staff of the laboratory network were not cut, the axing of leadership and administrative staff will bring its operations to a halt, a source said.

Kristy Pabilonia, executive director of clinical diagnostics for Colorado State University's Veterinary Health System, said she has relied on the center to take reports of cat infections that could be linked to pet food.

"It keeps me up at night thinking that there would be a chance that I wouldn't have someone to report to," she said.

The cuts are also likely to significantly disrupt efforts under way to develop bird flu testing infrastructure for aged artisan raw milk cheese, said Keith Poulsen, a veterinarian and director of the Wisconsin Veterinary Diagnostic Laboratory who has been involved in the effort.

Federal health officials have warned against the consumption of raw milk, which can carry a host of pathogens, because of the bird flu outbreak. Nearly one thousand U.S. dairy cattle herds have been infected with the virus over the past year. Kennedy has been a proponent of raw milk.

Coordinating bird flu testing through the national lab network is critical to tracking and managing the virus' spread, Poulsen said.

"You chop off the head of the leadership, and now we have to reinvent that wheel. That's not in our best interest," he said.

Bird flu has killed nearly 170 million chickens, turkeys and other birds in an ongoing outbreak that began in 2022 and has driven egg prices to all-time highs. Prices have dipped somewhat in recent weeks amid a lull in new infections and increased imports.