The Saint-Lazare fire department released a report Thursday.
It says that by the time firefighters arrived on the scene, the fire had already spread to the second floor of the kennel.
Firefighters put out the flames, but by the time they did, the 18 dogs inside the kennel were already dead from smoke inhalation.
The report says the exact cause of the fire is indeterminable, but it states it's clear it was an accident — probably due to an electrical problem.
"It's a tragedy. We can't really set blame anywhere. There was a fire — we have to unfortunately accept the fact that this happened," said Saint-Lazare mayor Robert Grimaudo.
"We can always take measures in the future to see what we can do to be more vigilant, and see if we can prevent such things from happening in the future, but it's just a terrible accident."
Family K9, owned by Nick Zevgolis, was not equipped with any smoke alarms or fire extinguishers — which is legal because nobody lives in the building.
Zevgolis's kennel was not registered with the Quebec government.
A new law that came into effect in November, requiring anyone who owns or boards 15 or more dogs or cats at any given time to have a permit. But a grace period extended to March 7, 2014, to obtain the licence means that Family K9 was not breaking the law.