An Ancaster, Ont. furniture plant lies in ruins after it errupted in flames early Tuesday, leading to a day-long battle for firefighters.  

Fire crews first responded to the blaze at Archmill House on Osprey Drive at 3 a.m. By the evening, firefighters were targeting hotspots at the plant.

The fire began inside and expanded into a three-alarm blaze by 6 a.m. A propane tank reportedly exploded, according to reports from the scene. Other, smallers blasts could also be heard. Several walls and part of the roof collapsed under the heat.

Glum workers could only watch as the source of their livelihood went up in flames.

The millwork manufacturing plant makes wooden cabinets and other interior furniture for homes and businesses. An employee of the plant who came to the scene of the fire after hearing about it on the news told CTV Toronto that it was a busy business.

"It's pretty sad. It's a place where we've been working for a long time," said another employee at the scene. "To see it go up in flames is sad for us and the owner."

At the height of the blaze, 70 firefighters battled the flames. At one point, firefighters were asked to pull back because of the fire's intensity.

"Conditions deteriorated rapidly inside the building where we had a lot of flame up in the roof area of the building (and) it became unsafe for firefighters to be inside," said John Verbeek of Hamilton Fire, explaining why crews were told it was unsafe to proceed.

The thick grey smoke could be seen as far as 20 kilometres away.

Two fire trucks were brought in from Hamilton's airport. Firefighters used them to spray foam inside the back door of the building to help dissipate the smoke and give crews inside the plant clearer visibility.

No one was inside when the fire broke out, according to officials. No injuries were reported.

A spokesperson for Hamilton Fire Services told CTV Toronto that enviromental officials monitored the air quality for toxins. Local homeowners and businesses were asked to keep their windows closed and to turn off their air conditioning as a precaution.

The worst of the smoke had dissipated by the noon hour.

The Fire Marshal's Office is investigating the incident.

With a report from CTV Toronto's John Musselman