The U.S. Department of Agriculture (USDA) said on Wednesday that all the ground beef samples sent to the National Veterinary Services Laboratories (NVSL) for PCR testing were negative for the H5N1 bird flu virus.

USDA’s Food Safety and Inspection Service (FSIS) collected 30 samples of ground beef from retail outlets in the states with dairy cattle herds that had tested positive for H5N1 at the time of sample collection.

"NVSL reported that all samples tested negative for H5N1. These results reaffirm that the meat supply is safe," the USDA added.

Federal authorities have been working to confirm the safety of milk and meat products after the detection of H5N1 in 34 dairy cattle herds across nine states since the end of March. Additionally, one case has been confirmed in a person in Texas.

The U.S. Food and Drug Administration said preliminary results of tests on additional dairy products show pasteurization inactivates the bird flu virus.

Both the U.S. Centers for Disease Control and Prevention and the World Health Organization have said the overall public health risk is low, but is higher for those with exposure to infected animals.

Scientists remain vigilant for any alterations in the H5N1 virus that could adapt it to spread easily among humans. The virus has been responsible for severe infections in people who have been in close proximity to wild birds or poultry.

It has consistently been considered a virus with the potential to cause a pandemic, and its spread to a new mammalian species is a cause for concern.