TORONTO — It's proving harder than anticipated to type the avian flu viruses wild ducks sampled in Canada were carrying because a number were co-infected with several strains, creating a viral "soup" that is difficult to separate down to its basic ingredients, government officials have admitted.

They say, however, that it appears that none of the viruses are highly pathogenic, a finding that would support the suggestion none of the birds were carrying the worrisome Asian H5N1 flu virus, which is a so-called high path virus.

"We can't say we don't have an H5N1," said Dr. Jim Clark, acting director of the animal health and production program for the Canadian Food Inspection Agency, the lead government agency on this work.

"That's a possibility. But we can say with reasonable certainty that H5N1, if it is there, it's not the high path Asiatic subtype that's going on in Southeast Asia."

Highly pathogenic avian influenza viruses are lethal to domestic poultry. Viruses that are of low pathogenicity do not kill domestic flocks, though they can lead to a decline in egg production.

It has been over two weeks since federal officials said they had found H5 viruses in wild ducks sampled as part of a national surveillance project aimed at finding out what avian flu viruses might be present in this country.

Those findings were from sampling sites in Manitoba and Quebec only. Later, British Columbia authorities revealed they too had found H5 viruses. The results of sampling done in Ontario, Alberta and Atlantic Canada are still pending, Clark said.

At the time of the announcement, authorities believed they would be able to fully type the viruses -- determining what neuraminidases or Ns the viruses carried -- within days. But that estimate has proved to be too optimistic, because of the concurrent infections in many of the birds.

Dr. Frank Plummer, scientific director of the Public Health Agency of Canada's national microbiology laboratory, said laboratory technicians are finding a variety of neuraminidases, including N1s.

(To date the scientific world has identified nine different neuraminidases and 16 hemagglutinins -- the H in a flu virus's name -- that theoretically can come together in 144 possible combinations.)

"We're finding lots of different ones, including N1s. ... which is really not surprising because we've known from before that those different antigenic types are out there," Plummer said from Winnipeg.

"But knowing which goes with which is impossible from the soups that we have right now. It's just going to take some more time to sort it out."

The confusing findings are of little surprise to avian influenza researchers.

"It's typical," David Stallknecht, an avian influenza specialist at the University of Georgia's college of veterinary medicine, said of the viral melange Clark and Plummer described.

"What you get is a real soup. You get a lot of different serotypes."

Plummer said his lab has been doing genetic sequencing on genes from the viruses, but that isn't helping to clarify the picture.

"The sequencing's been problematic because the RNA is mixed up," he said.

"And it makes it difficult because you get two sets -- or three sets -- of sequences from this one sample. And they're all jumbled up. It's very hard to sort out."

"Say if you get an H5 and an N1, and an H7 and an N3 from a sample, you don't know which H goes with which N."

Clark said final results could be some time off - and it is conceivable all the viruses may never be fully subtyped.

"It could be months. Let's face it. Trying to get that pure virus may prove to be completely elusive. We may never get it."