By P.J. Huffstutter

CHICAGO (Reuters) - Quality Egg LLC and two top executives on Tuesday admitted to selling substandard eggs containing a "poisonous" substance and bribing a federal inspector in a food-safety scandal that sickened tens of thousands, the U.S. Department of Justice said.

The Iowa-based company, once among the United States' largest producers of shelled chicken eggs, along with owners Austin and Peter DeCoster, pleaded guilty Tuesday to federal charges in connection with the massive nationwide salmonella outbreak in 2010.

An estimated 62,000 consumers fell ill during the outbreak after eating shell eggs tainted with Salmonella Enteriditis.

Quality Egg pleaded guilty to selling eggs mislabeled to hide how old they were; giving cash bribes to a U.S. Department of Agriculture inspector to approve and allow poor-quality chicken eggs to be sold to the public; and introducing adulterated food into interstate commerce, according to the DOJ.

The company admitted "its employees affixed labels to egg shipments that indicated false expiration dates with the intent to mislead state regulators and retail egg customers regarding the true age of the eggs," according to a Justice Department statement.

Tuesday's plea hearing was held in U.S. District Court in Sioux City, Iowa.

The company has agreed to pay about $6.8 million in fines, according to consent agreements filed in federal court. The ultimate fine will be determined by the court at a sentencing hearing to be set at a later date, according to a Justice Department spokesman.

Attorneys for Austin "Jack" DeCoster, 79, his son Peter, 51, and the company could not immediately be reached for.

The DeCosters also each pleaded guilty to misdemeanor charges of introducing adulterated food into interstate commerce. Each of the men paid the court $100,000, to be applied toward fines.

The DeCosters could each face up to a year in prison and pay additional restitution to people injured in the salmonella outbreak, according to the court filings. Both men were released on bond, pending a sentencing hearing before U.S. District Judge Mark W. Bennett.

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Neither sentencing hearing has been scheduled, according to the Justice Department.

The case is U.S. v Quality Egg, LLC, Austin DeCoster and Peter DeCoster, U.S. District Court, Northern District of Iowa, No. 14-cr-3024.

(Reporting by P.J. Huffstutter; editing by Andrew Hay)