Police are treating a major fire at an Alliston feed mill as a criminal investigation.

OPP Const. Harry Lawrenson said no one is in custody at this point but that police may have more details as the day progresses.

The fire broke out around 2 a.m. on Albert Street, completely engulfing the working feed mill in flames. Firefighters evacuated several nearby homes and residential buildings as they battled the blaze.

Authorities closed down traffic in the area to allow crews to battle the fire.

Firefighters were on site for hours trying to get the blaze under control.

"This is a feed mill so they don't deal with the fertilizers, so from a Hazmat perspective it's a much lower incident. Obviously if we were dealing with the fertilizer industry then we would have more concerns. This was corn seeds and some dog food," a firefighter said at the scene.

Residents in the area said they were woken up to the sound of the blaze.

"I came out and we were sitting on the balcony and all of a sudden the flames just got bigger. The whole steele was in flames," one nearby resident told CTV Toronto.

"It's a lovely historical building and it is a shame that it's gone. Hopefully they can put it back up again," another resident said Friday.

An investigator from the Office of the Fire Marshal has been dispatched to the scene.