MONTGOMERY, Ala. (AP) — After confirming the presence of highly pathogenic avian flu in a flock of chickens, nearly 48,000 birds were killed at a north Alabama farm, state agriculture officials said.

A Marshall County commercial pullet farm — one that raises chicks from hatching until they are ready to produce eggs when they are moved to a laying barn — was placed under quarantine after samples were confirmed positive for HPAI, the Alabama Department of Agriculture & Industries announced Friday.

HPAI is highly contagious to birds but considered low risk to humans and the virus is not considered a threat to food safety, the department said.

“It is critical for commercial and backyard poultry operations to remain alert and closely monitor the health of their poultry,” Alabama Agriculture Commissioner Rick Pate and State Veterinarian Tony Frazier said in a joint statement. “The HPAI infected flock in Marshall County reinforces the need to continue following strict biosecurity measures, including keeping birds enclosed without access to wild birds or other domestic flocks.”

All poultry within a 6.2-mile (10-kilometer) radius of the farm are being tested and monitored, al.com reported. However, no other flocks have experienced an uptick in deaths, the news site reports.

HPAI symptoms in birds include a sudden increase in bird deaths in the flock; watery and green diarrhea; lack of energy and poor appetite and a drop in egg production or soft or thin-shelled, misshaped eggs.

The detection of the virus in Marshall County comes a week after HPAI was confirmed in an upland gamebird farm in Chilton County. All poultry there — nearly 296,500 birds — were affected and all will be killed, the department said.

It was not immediately clear if the cases at both farms were connected.

The department urged the commercial poultry industry and backyard flock owners to increase biosecurity measures to protect their operations from HPAI by, among other things, cleaning vehicles and equipment; changing clothes upon contact with birds and limiting unnecessary visitors.

Sick or dead wild birds should be reported to the Alabama Department of Natural Resources and Conservation, while sick or dead domestic birds and poultry should be reported to the Alabama Department of Agriculture and Industries’ Poultry Unit.