EMBDEN – Investigators from the State Fire Marshal’s Office Friday sought the cause of a fire that destroyed a salmon hatchery in Embden, killing nearly 3 million juvenile fish.

Firefighters from seven towns battled the Thursday night fire at the Kennebec Hatchery of Atlantic Salmon of Maine. No injuries were reported.

The fire started in the mechanical room containing the pumping system that supplied fresh water and oxygen to about 100 circular tanks holding the juvenile salmon.

The company said the salmon suffocated when the fire caused the electrical system to fail, cutting off oxygen to the freshwater tanks. Officials had no immediate estimate of the monetary loss.

The Kennebec Hatchery contained 740,000 Atlantic salmon smolt ready for transfer to ocean pens, as well as 2.1 million Atlantic salmon fry that were to be stocked in pens this fall and next spring.

The fire was the second setback within a week to Maine’s largest aquaculture business.

On May 9, a federal judge in Portland found the company in civil contempt for violating a court order barring it from stocking smolt in its pens.

The order arose from an environmental lawsuit that accused Atlantic Salmon of Maine and another Washington County salmon farming business of discharging pollutants such as excess feed, feces and medication into the ocean without a permit.

U.S. District Judge Gene Carter ruled against the companies but has yet to announce penalties or remedial actions.

Atlantic Salmon of Maine also operates a smaller hatchery in Oquossoc, near Rangeley.