Avian influenza has so far been found on eighteen commercial poultry farms in Fraser Valley, British Columbia, as authorities battle to control the spread of the disease.

"The disease is spreading and it's spreading quickly," Brian Evans, of the Canadian Food Inspection Agency, was quoted by the Canadian Press as saying. 

Evans said the disease had probably been brought to the region by wild waterfowl but was now being spread by human activity.

"We cannot be certain at this time that we are on top of the situation. Further time will be required and we are working creatively, flexibly and passionately to consider new protocols and industry approaches," Evans said.

Around 400,000 chickens have been slaughtered already in a bid to halt the spread of the disease, but the latest discoveries are likely to lead to further culls.

Some poultry producers have suggested a cull of the entire poultry population of Fraser Valley, which would include around 16 million birds.

The poultry industry in British Columbia is worth more than C$800m (US$609.6m) per year and the bulk of production is situated in the Fraser Valley.