TORONTO -- City officials said Wednesday they are investigating to try and understand how a COVID-19 outbreak occurred at an emergency child care centre after an eight-month-old child and four staff members tested positive for the virus.

“City staff and Toronto Public Health took immediate action to close this facility once the workers tested positive and they are continuing to investigate why this happened and where it happened,” Mayor John Tory said at a news conference.

He called the outbreak “a sad reminder of the dangers of COVID-19 and some of its continuing unknowns.”

Tory said the city is investigating the outbreak to try and take whatever lessons possible.

“As part of the investigation I’ve asked that we determine exactly what happened here and how we can strengthen the already stringent procedures we have in place to try and keep COVID out of these child care centers,” Tory said. “I can assure the families relying on these child care centres and the people of Toronto that the very highest standards were put in place from Day One to try and prevent this kind of outbreak, but obviously we have more to learn.”

The city announced late Tuesday night that it would close the Jesse Ketchum Early Learning and Child Care Centre, near Davenport Road and Bay Street, for 14 days after three staff members tested positive for COVID-19.

On Wednesday, health officials said that an additional staff member has now tested positive for the virus, as well as an eight-month-old child who attended the centre. Test results are still pending for one staff member and another child tested negative.

According to city officials, the centre was first alerted to the possibility of an outbreak when two staff members called in sick. They were told to stay home, as per protocol.

Officials said the child who tested positive was screened for symptoms when they attended the centre and was not found to have any. The parents of that child later informed the centre that the child had developed symptoms and they were advised to get the child tested.

Speaking with reporters Wednesday, Toronto’s Medical Officer of Health Dr. Eileen de Villa said public health officials are trying to understand how the outbreak occurred.

“We need to let the investigation proceed, understand what the circumstances might have been and then take action as necessary,” de Villa said.

She said the infection-prevention measures implemented at the child care facilities are similar to those being implemented in health care settings around the city.

“Those protections, those measures that are being put into place are based upon the best available science that we have in regards to this virus at this time. So we are continuing to learn, we are always assessing practice and trying to do better and better each time,” de Villa said.

Jesse Ketchum is one of seven city-run child care facilities that have been providing care to the children of essential workers, many of them health-care workers.

Others staff and children who attended the facility are being advised to stay home for two weeks from their last day at the centre.

The city said that the 58 kids who attend the centre are also barred from attending other city-run emergency childcare facilities as a precaution. That means that their parents, most of whom are health-care workers or first responders, will have to find alternative arrangements or take time off from their jobs.

Tory told CP24 earlier Wednesday that he is “deeply concerned” by the outbreak and is committed to seeing what can be done to prevent similar outbreaks at the six other city-run centres.

“It is of deep concern to us first and foremost because there is a lot of kids that were potentially affected that now have to stay home and staff,” Tory said in an interview with CP24. “We are investigating it. I have only received the most preliminary of information because it just came to light late yesterday but we will have to see what we can learn from it in terms of the other emergency childcare centres we are operating.”

The emergency childcare centre first opened on March 31 after the province announced it would provide funding to operate facilities for the children of thousands of health-care workers and first responders during the COVID-19 pandemic.

At the time, the province said that a number of precautions would be taken in the facilities, including daily screening of children and staff, increased disinfection and reduced group sizes.

The city has said that the Jesse Ketchum Early Learning and Child Care Centre “will undergo a deep cleaning” and will only reopen once approval is granted by Toronto Public Health.

The centre is grappling with the outbreak as the province expands the list of essential workers who are eligible for emergency child care.