The fire department received a call about the possible spill in the Fraser Avenue apartment building in the afternoon. One floor of the building was evacuated around 3 p.m. local time, and the children were taken to hospital.
Two children, two and six years old, were taken to the Stollery Children’s Hospital in Edmonton. Two others, aged four and seven, remain in a Fort McMurray hospital.
The mother of the eight-month-old is under observation in the Fort McMurray hospital.
The RCMP, who are still investigating, haven't yet determined the exact nature of the fumigant.
All other building tenants were allowed to return home around 6:30 p.m. Sunday after air-quality testing determined it was safe.