Firefighters began tearing into the old Black Clawson warehouse Sunday, trying to extinguish a stubborn blaze that began Saturday night.
Watertown Fire Chief Dan Gaumont said the fire will likely continue to smolder for another day or more.
"We're still putting water on the building," Gaumont told 7 News. "The building is unstable, unsafe right now."
"We're gonna be here for a couple, three days anyway."
The fire struck the building off Pearl Street between 5 and 5:30 pm Saturday. The blaze caused a huge cloud of black smoke that could be seen in much of Jefferson County.
The fire caused a major power outage, and forced firefighters to evacuate near-by homes, including six to eight homes on Water Street. Most people returned to their homes by Sunday morning, but fire officials encouraged people who don't live in the area to avoid it.
Because the roof collapsed as the fire spread, firefighters were unable to get to the fire inside the structure.
"When the building collapsed in on itself, it's now hidden the fire under pockets of debris," Gaumont said.
Power was restored to 4100 people in the Watertown area shortly after 8:30 pm Saturday.
Pearl Street and Water Street were both closed in the area of the fire Saturday, access to the streets at the fire scene was still limited Sunday.
Three firefighters were injured Saturday, fire officials said, though none of the injuries were life threatening - one suffered smoke inhalation, another dehydration and a third stepped in a hole.
This Fire started approximately 5pm, Saturday, July 2, 2005, crews are still there at this hour pouring 1000's of gallons of water onto hotspots.
Chief Gaumont said he believes toxic chemicals leaked into the river, as firefighters poured thousands of gallons of water into the plant. Old facilities like Black Clawson typically used dangerous or toxic chemicals in industrial processes. Gaumont said he has notified the Department of Environmental Conservation.
"That runoff went down into the river. We have no idea what may be being put into the river."
At first there was confusion about whether the outage was related to the fire. Bystanders saw electrical flashes, while city officials said they were told the two were NOT related.
Ultimately, Niagara Mohawk said the two were related. There were reports the outage was a consequence of Niagara Mohawk having to shut down electricity in the area around the fire scene.
It was not clear Sunday who owns the building; Michael Lynch, who operated a machine shop inside the structure, said he sends his rent checks to a real estate agent.
In addition, the property was listed on the city's most recent tax auction.
Scores of bystanders gathered on Factory and Huntington Streets.