The Hospital for Sick Children is reporting several cases of a rare multisystem inflammatory syndrome in children, similar to clusters of the condition seen the U.S., Europe and other parts of Canada.
It's believed the illness may be linked to COVID-19.
The hospital's associate paediatrician-in-chief told CTV News they have seen about 20 cases in the last three to four weeks.
The illness is similar to Kawasaki Disease and as many as 80 percent of cases are thought to be in children under five.
However, Sick Kids is reporting cases in patients as old as teenagers.
Symptoms include rashes, swelling, vomiting and high fever.
None of the children in Toronto tested positive for COVID-19 but in cases elsewhere, many tested positive for antibodies, suggesting they may have been infected weeks earlier.