A fire that tore through floors in a North York highrise last November, killing one man and injuring six other residents, was caused by a space heater that was left running dangerously close to combustible material, Ontario’s Fire Marshal says.

“A space heater in one of the apartment’s bedrooms was too close to combustibles and caused the fire in which one person tragically perished and six others were injured,” the Fire Marshal’s office said Tuesday.

The fire marshal said that people inside the unit where the blaze started ignored the first smoke alarm that went off, dismissing it as false.

Richard Derstroff of the Fire Marshal's Office said the fire built in size for "quite some time" before anyone discovered it.

The tenants also tried to put out the fire themselves instead of leaving and calling 911.

It wasn’t until another smoke alarm in the common hallway of the floor where the fire started went off that fire services were notified.

By then it was too late.

Fifty-seven-year-old Nam Tu Huy Vu was on the eighth floor of the building on Gosford Boulevard, near Jane Street and Shoreham Drive on Nov. 15.

A close friend of his told CTV News Toronto that Vu was leaving his unit when they ran into thick smoke in the hallway.

The friend said Vu went back into his unit, possibly to retrieve some belongings.

That was the last time he was seen alive.

He was found on the balcony of his unit by firefighters and later pronounced dead.

The fire spread through other units, eventually injuring six other people and reaching five alarms before it was knocked down.

Derstroff told CP24 the space heater ignited a mattress and bedding, which then grew into a very large fire.

A large number of tenants in the building were forced out for weeks while the building was repaired.

In December, city engineers said twelve units required significant repairs before they could be re-occupied.