Four more children have been diagnosed with salmonella since yesterday, as the city’s public health department continues to investigate an outbreak of food poisoning that appears to have spread through a caterer serving hot lunches at schools and daycares.

The Ottawa Citizen reports there have now been 27 lab-confirmed cases of the food-poisoning bacteria since Public Health declared an outbreak early this week, including 23 children and four adults. (Two of the adults are included in the tally even though their cases are believed to be unrelated.) Friday afternoon, the health department also added two schools to the list of those where children have become sick: Bayvew Public School and Ecole élémentaire Des Sentiers.

Investigators are still analysing food from a kitchen run by a franchise of The Lunch Lady, trying to confirm suspicions that its meat lasagna and beef tacos were contaminated. All six schools and one daycare where children are known to have got sick are served by one franchise of The Lunch Lady, which delivers meals to kids whose parents pay for the service.

The results of the lab analysis are expected to take a few more days, perhaps even until next Wednesday, said Public Health spokesman John Steinbachs. Bacterial cultures take time to grow, and they then have to be compared with samples from afflicted patients to see if they match.

In the meantime, two Lunch Lady kitchens — the one on Boyd Avenue where investigators have been concentrating their efforts, and another in Kanata — are closed, said their owner, Jonathan Morris.

“We don’t know what the source of the contamination is, and until we do, we’re not going to be making or serving food,” he said. Parents whose children get meals from those kitchens will have to make other arrangements for at least next week, Morris said.

“It’s harder as a parent than it is as a business owner,” Morris said. “I’m a parent, most of my staff are parents, and we serve food to a lot of them. These kids getting sick, that’s what’s, well, that’s what making me sick. The business is … that’s not even secondary.”