The fire-gutted remains of the Prairie Mushroom Ltd. plant in Sherwood Park. ((CBC))

More than 60 people have been left without jobs after fire gutted a mushroom-growing operation in Sherwood Park, just east of Edmonton, early Saturday.

The fire at the Prairie Mushrooms Ltd. plant at Range Road 232, north of the Yellowhead Highway, destroyed a warehouse the size of four football fields.

Dozens of firefighter crews from Strathcona County, Fort Saskatchewan and Edmonton were called in to fight the blaze, which according to fire officials was the biggest in the county in more than a decade.

The fire did not damage a second, smaller facility nearby, which will limit the job loss, said company owner Don Kostelyk.

"On our whole site, which is two buildings, we have about 115 employees and probably 60 to 70 of them will have to be laid off. I'm sure they're a little bit shocked, as we are," Kostelyk said.

The cause of the fire, which caused about $10 million in damages, is still unknown.

The loss will be covered by insurance, Kostelyk said, who hopes to rebuild in 12 to 18 months.

The plant produced more than 45,000 kilograms of mushrooms each week for stores in Edmonton, Calgary, northern Alberta and some parts of British Columbia.