A major electrical fire at Hamilton's Canada Bread plant in Glanbrook on Monday night caused an estimated $500,000 in damage.

Firefighters managed to put out the flames, but not before the fire made one transformer attached to the building's south side a "complete write off," said fire department spokesman Claudio Mostacci. Another transformer also suffered minor damage in the fire.

The cause of the fire was deemed to be electrical, Mostacci said, and Hydro One officials are now investigating.

Canada Bread spokeswoman Sylvia Sicuso said the Nebo Road plant isn't operational yet and the company is still assessing the damage. Company officials were only granted access to the building in the early afternoon, she said, and that there's still cleanup work to be done until work can resume there.

Sicuso said other bread plants in the region have ramped up their operations, so GTA customers won't notice a shortage of bread.

About 100 Canada Bread workers were forced from the building when the fire broke out around 6 p.m. The workers took shelter in three transit buses that were sent to the scene.

“All the workers and staff are accounted for and out of the building,” Mostacci told CBC Hamilton on Monday evening.

One firefighter suffered a minor hand injury, requiring stitches, but is recovering well. In total, some 20 firefighting units were dispatched to the scene, 15 of which were battling the fire at its peak.

Hamilton was hit by heavy winds on Monday evening, with gusts of over 90 km/h. Mostacci couldn't say if the winds played any role in how the fire started.

Canada Bread executives expected the factory to be down at least 12 hours while they evaluate the scope of the damage, Mostacci said.

Paramedics responded to a call from someone outside the factory location shortly before the fire broke out. Paramedics transported a patient from the location in "serious but stable condition," but it's not known at this time if that call was in any way connected to the fire, said Hamilton Paramedic Service deputy chief Russ Crocker. The patient was not a Canada Bread employee, Mostacci said.

The $100-million Canada bread facility in Hamilton is touted as Canada’s largest bakery plant. Maple Leaf Foods opened the state-of-the-art bakery in 2010. Maple Leaf's decision to build the plant here was a major economic development catch for the city.

Full operation at the plant only started last year. It has over 300 full time workers. Earlier this year, Maple Leaf sold its share in Canada Bread to Mexican-based Grupo Bimbo.