SAN FRANCISCO -- Two chickens at a live bird market in San Francisco, US state of California, tested positive for H5N1 bird flu last month, authorities announced on Monday.

The San Francisco Department of Public Health reported that state health officials discovered the infected, asymptomatic birds during a routine monitoring program conducted by the California Department of Food and Agriculture.

"There is no threat to public health at this time ... There have been no human cases," said George Han, the director of communicable disease prevention & control at the San Francisco Department of Public Health.

Health officials said no public exposure occurred, no people reported symptoms, and the market has reopened.

In response to the bird market detection, WastewaterSCAN, a national initiative monitoring infectious diseases through municipal wastewater, began testing San Francisco's wastewater for H5N1.

Initial tests detected fragments of H5N1 genetic material, making San Francisco the only municipality in California with a positive bird flu detection, according to WastewaterSCAN.