The cause of the massive industrial fire at Vinyl Works Canada in Port Colborne is believed to be accidental.
Deputy Fire Chief Mike Bendia updating the media late this afternoon saying the investigation by the Fire Marshall's office, Port Colborne Fire, and NRP has been completed.
The fire started in the structures' south west quadrant Tuesday morning.
Investigators say the blaze was sparked a catastrophic failure of the electrical system.
The damage estimated is now over 3 million dollars.
Earlier today, fire officials gave residents in the area the green light to return to their usual outdoor activities.
No one was hurt.