NEW YORK — A new study that recreated commercial pasteurization in a government lab provides reassurance that heat treatment kills bird flu virus in cow’s milk, U.S. officials said Friday.

When the bird flu known as H5N1 was first detected in U.S. dairy cows earlier this year, there were no studies of whether heat treatment killed the virus in cows milk. But officials were comforted by studies that showed the pasteurization of eggs — which involves heating at a lower temperature and for a shorter amount of time – worked, said the Food and Drug Administration’s Donald Prater.

A study in April found that there was no evidence of infectious, live virus in store-bought samples of pasteurized milk, though they did contain dead remnants of it. Some later small studies that attempted to simulate pasteurization showed mixed results.

The new study was done at a federal research center in Athens, Georgia, using custom equipment that tried to more completely recreate commercial pasteurization.

It also allowed sampling at different stages in the process. The milk goes through several heating steps before being flash-heated, and the study found the virus was inactivated even before it hit the 161-degree, 15-or-more-seconds “flash pasteurization” stage that is considered the key step in making milk safe.

“This information really fills an important gap in our understanding of how commercial pasteurization inactivates the virus,” Prater said.