Left Hand Brewing filed a lawsuit against a former yeast supplier claiming the company sold the brewer a strain that contaminated $2 million worth of beer.

Left Hand Brewing alleges White Labs Incorporated sold a strain that caused beers to continue to ferment after being bottled. Customers complained of excessive, built up pressure in the bottles.

Left Hand says the secondary fermentation also increased the alcohol content, affecting the overall quality of several types of beer.

The brewery says it recalled its Milk Stout Nitro, Extrovert IPA and Warrior Fresh Hop IPA and shut down production for two weeks to clean and rebuild.

In the lawsuit filed in Boulder County District Court, Left Hand Brewing claims they ordered extensive laboratory testing to confirm the White Labs yeast was causing the secondary fermentation. The lawsuit claims the Colorado Department of Public Health and Environment confirmed that the White Labs yeast had been contaminated by Diastaticus.

White Labs Inc. shared this statement with 9NEWS:

“The case, which is being defended by our lawyers, claims that Left Hand Brewery received a batch of contaminated yeast from us in 2016. There is no specific proof on where the contamination originated from, as each White Labs culture undergoes a rigorous testing process from start to finish, which includes 61 quality checkpoints throughout the propagation cycle. Additionally, every batch of yeast is tested to confirm it is contamination free prior to shipping. We cannot provide further comment due to the ongoing litigation.”

Left Hand's co-founder and CEO provided a statement but can't answer questions citing the lawsuit.

“It is unfortunate we had to file a lawsuit, but we didn’t have a choice. As an employee-owned brewery, the fate of our brand and employee livelihood was compromised and we are asking White Labs to take responsibility for the quality of their product and stand behind their guarantee.”