Police believe a murder-suicide plot may be behind a fatal fire in Toronto's Don Mills community Saturday evening.

Investigators combed a townhouse complex Sunday looking for clues on what sparked a massive blaze. They found the remains of two bodies inside the Green Belt Drive home, in the Lawrence Avenue and Don Mills Road area.

The bodies were so badly burned, forensic tests need to be completed before police can confirm whether they are male or female.

A three-year-old boy who lived inside the home was found wandering outside the house while the property was being ripped apart by intense flames. He was taken to safety by police at the scene.

A fourth person, an adult, who also lived at the home is still missing.

The superintendent who manages the complex told CTV Toronto someone knocked on his door around the supper hour on Saturday. When he opened the door, he found the boy alone carrying an envelope.

"The boy was saying, 'da da,' that is Hungarian language, because his mother is Hungarian," he said. "He had a note with him. The note I give to the police."

Police say the note said, "This is my confession. There is a tape in the car."

However, investigators said the tape recorder in the car that was parked in the garage does not work.

By the time the superintendent went to knock on the boy's door after finding him on his doorstep, he realized the complex was rapidly burning and the door to the unit was locked tight.

Three adults lived inside the home with the boy, including the boy's father, his wife and her 70-year-old mother.

When authorities arrived at the scene, there was a strong smell of gasoline, police told CTV Toronto.

Police say they have responded to calls at the residence before for reports of domestic violence.

Tenants who lived in other units of the complex were able to escape unharmed.

The building was badly damaged in the blaze, which required about 100 firefighters and more than 20 trucks to extinguish the flames.

"It moved vertically through several units," Andrew Kostiuk, a Toronto Fire official, told CTV Toronto from the scene Saturday night.

Kostiuk called the fire "suspicious."

Aaron Kelman, a 29-year-old bystander, told CTV Toronto he noticed the fire when he heard a loud noise from across the street.

"The fire was massive," he said. "Everything was engulfed all at once. There was tons of smoke and then it was spreading rapidly.

One witness said he saw the little boy by himself outside the home.

"We noticed a little kid trying to get back into the house that was on fire," said witness Leszek Diadyk. "We pulled him away from the house and started knocking on all the doors trying to get everyone out."

With a report from CTV Toronto's Carol Charles and Austin Delaney