Officials estimated the order covers 10 farms and 33 smaller home flocks with a total of 275,000 birds. All are within a three-mile radius of where the first case of the disease was discovered.

Five farms with a total of 90,000 birds have already been ordered to kill their chickens after flu was detected in their flocks.

Although the disease has not been detected at any of the farms covered by the new order, officials were worried about the potential of additional disease spread if the birds were allowed to remain.

"You can make the analogy that it is like removing the fuel," said Cornelius Kiley, a veterinarian with the Canadian Food Inspection Agency.

Officials warned that since the virus may also have been spread by wild birds, they cannot rule out that it could reach farms outside of the five-kilometer "high risk" area covered by the order.

Officials have already imposed bans on transporting chickens through and out of the area in the Fraser Valley, but British Columbia is not a major international exporter of poultry products.