The onsite investigation of the major fire that caused $1 million in damage to a west Windsor plastics factory is complete.

Representatives from the Office of the Ontario Fire Marshal say the full investigation could take up to three months. Materials are being sent for forensic testing.

The blaze started in the yard, at the exterior of the building, according to Jeff Minten, fire investigations supervisor with the Ontario Fire Marshal.

The Windsor police investigation is also complete, and the site has been turned over to the Sprucewood Industries owner.

The fire started just after 3 p.m. on Tuesday at 730 Sprucewood Ave. Thick black smoke billowed from the site for hours as firefighters were forced to let it burn.

Officials say the fire is not considered suspicious.