An 18-month-old Markham toddler is fighting for his life after falling into a backyard pool.

The child had no vital signs when he was discovered by his foster father at 83 Pringle Avenue near Highway 7 and the Ninth Line in Markham.

The child was revived and rushed to Stouffville Hospital by paramedics shortly before 1 p.m.

He has since been airlifted to McMaster University Medical Centre in Hamilton.

York police believe the child wandered outside after discovering a door leading from the house to the pool deck was left open.

The boy is one of several foster children living at the residence.

Adults and two of the family's biological children were at home during the accident.

An investigation is under way to determine how the child wandered out into the pool area.

With a report from CTV's Jim Junkin