DENVER — Eric and Ryan Jensen, the two brothers who operated Jensen Farms, the cantaloupe processing operation that was the source of a Listeria outbreak in 2011 that caused 33 deaths and 147 illnesses, were charged on Monday for introducing adulterated food into interstate commerce. Both face six counts apiece and, if convicted, each faces up to one year in federal prison, and a fine of up to $250,000 per charge.

“As this case so tragically reminds us, food processors play a critical role in ensuring that our food is safe,” said U.S. Attorney John Walsh. “They bear a special responsibility to ensure that the food they produce and sell is not dangerous to the public. Where they fail to live up to that responsibility, and as these charges demonstrate, this office and the Food and Drug Administration have a responsibility to act forcefully to enforce the law.”

Court documents state the defendants set up and maintained a processing center where cantaloupes were taken from the field and transferred to a conveyor system for cleaning, cooling and packaging. The equipment should have worked in such a way that the cantaloupe would be washed with sufficient anti-bacterial solutions so that the fruit was cleaned of bacteria in the process, according to the Department of Justice.

In May of 2011 the Jensen brothers allegedly changed the cantaloupe cleaning system. The new system, built to clean potatoes, was installed, and was to include a catch pan to which a chlorine spray could be included to clean the fruit of bacteria. The chlorine spray, however, was never used. The defendants were aware that their cantaloupes could be contaminated with harmful bacteria if not sufficiently washed. The chlorine spray, if used, would have reduced the risk of microbial contamination of the fruit.

Investigation by the Food and Drug Administration and the Centers for Disease Control and Prevention determined that the defendants failed to adequately clean their cantaloupe. The actions allegedly resulted in at least six shipments of cantaloupe contaminated with Listeria monocytogenes being sent to 28 different states.

“U.S. consumers should demand the highest standards of food safety and integrity,” said Patrick J. Holland, special agent in charge of the F.D.A. office of criminal investigations, Kansas City field office. “The filing of criminal charges in this deadly outbreak sends the message that absolute care must be taken to ensure that deadly pathogens do not enter our food supply chain.”