Up to 30% of the shrimp and prawns found in British Colombia (BC) is tainted with the E-coli bacteria - but consumers have not been informed of the contamination.

The Canadian Food Inspection Agency (CFIA) first discovered the bacteria during a routine audit of a Sunshine Coast processing facility last year. Scientists from Fisheries and Oceans Canada have since confirmed however that the source of contamination was not, as was initially thought, unhygienic processing or catching methods. Instead, they found that E-coli was already present in 15-30% of the sampled prawns and shrimp caught in the coastal waters.

Biologist Jim Morrison explained to The Vancouver Province that this is the first evidence of such contamination: "This is very much a surprise to us and unexpected."

Scientists are still unsure how contamination occurred, but have said that it may have come from birds, seals, dolphins or from human and onshore animal's excrement that had been washed into the sea.

So far, fishermen and wholesalers in the C$40m BC industry have received warnings, but consumers were not informed of the presence of the potentially lethal bacteria.

Defending the policy of limited notification, the CFIA's Klaus Schallie was quoted in The Vancouver Province as saying: "We identified a problem that had a potential. And it's been addressed and we think it's been appropriately addressed."

Health officials have warned consumers to thoroughly cook all shellfish products, and purchase them from licensed distributors, in order to ensure that they are safe. No illnesses caused by the E-coli bacteria have yet been linked to eating shrimp and prawns from the BC coastal waters.