The U.S. Food and Drug Administration said Tuesday that samples of pasteurized milk had tested positive for remnants of the bird flu virus that has infected dairy cows.

The agency stressed that the material is inactivated and that the findings “do not represent actual virus that may be a risk to consumers.” Officials added that they're continuing to study the issue.

“To date, we have seen nothing that would change our assessment that the commercial milk supply is safe,” the FDA said in a statement.

The announcement comes nearly a month after an avian influenza virus that has sickened millions of wild and commercial birds in recent years was detected in U.S. dairy cows in at least eight states. The U.S. Department of Agriculture says nearly 33 herds have been affected to date.

FDA officials didn't indicate how many samples they tested or where they were obtained.

The lab test they used would have detected viral genetic material even after live virus was killed by pasteurization, or heat treatment, said Lee-Ann Jaykus, an emeritus food microbiologist and virologist at North Carolina State University

“There is no evidence to date that this is infectious virus and the FDA is following up on that,” Jaykus said.