Two Colorado men whose farm shipped tainted cantaloupes across the nation have pleaded guilty to multiple charges related to a food poisoning outbreak.

Eric and Ryan Jensen faced charges of adulteration of a food. They face up to six years in prison and $1.5 million in fines.

Jensen Farms shipped at least six shipments of cantaloupes in 2011 that were not sterilized allowing them to become infected with the listeria bacteria. The fruit sickened people from California to Virginia resulting in 33 deaths.

“The defendants have now admitted that they failed to protect the public from deadly bacteria on their cantaloupe, in violation of the law and critical USDA requirements,” U.S. Attorney John Walsh said in a statement.

The USDA had found the brothers installed a system at their farm to sterilize melons with a chlorine spray. The system, that was designed to be used to sterilize potatoes, was never put into service by the farm.

Sentencing for the two men is in January.