About one in five samples of commercial milk in the U.S. tested positive for traces of bird flu in a national survey, with a greater proportion coming from areas with infected herds, the U.S. Food and Drug Administration said.

There is no evidence that the milk poses a danger or that a live virus is present, the regulator has said.

The FDA said late Thursday that additional testing is required to determine whether the intact pathogen is still present and if it remains infectious.

The agency said earlier this week that if the milk is heated to a specific temperature, it remains safe for human consumption as the process kills harmful bacteria and viruses.

Eight states in the U.S. have confirmed cases of bird flu in dairy cattle, according to the U.S. Department of Agriculture.

Only one person - a Texas farm worker - has been one confirmed to have bird flu. The patient's only symptom was eye inflammation, according to the state's health department.

(Reporting by Leroy Leo in Bengaluru; Editing by Tasim Zahid)