Dr Tom Kosatsky, the director of Environmental Health Services, said inspectors are trying to determine where the smoked salmon nuggets were produced, where the contamination took place and whether a recall is necessary.
"Where positive samples occur, there is concern, and there is action that takes place," said Dr Kosatsky.
CBC News bought the salmon nuggets at Longliner Seafoods on Granville Island. The manager there said they were smoked at a facility in Maple Ridge.
The Listeria bacteria was detected when CBC News bought a selection of deli meats and smoked salmon from nine stores around Vancouver and had them tested at a food microbiology lab at UBC.
On Tuesday, CBC revealed there was no Listeria on the meats, but two smoked salmon samples had strains of the bacteria, including one sample that had the toxic Listeria monocytogenes strain.
The bacteria was detected at a level low enough it wouldn't trigger a recall in Canada, but some countries, such as the US, have zero tolerance for any detectable levels of Listeria.
The results of the CBC News investigation match the results of an unreleased study by the BC Centre for Disease Control that also found Listeria in smoked salmon from up to five producers in BC.
The study looked at 293 samples of ready-to-eat foods — including meat, dairy and fish — purchased in BC between August and October 2009.
It found potentially toxic Listeria bacteria in 18 per cent of ready-to-eat fish products tested in BC. All of the contaminated fish was smoked salmon, the study found. It also concluded fish processing facilities need more scrutiny.
The results triggered at least one recall in November 2009, of Smoked Salmon Cream Cheese Log and Maple Salmon Nuggets from Classic Smokehouse Inc.