Source: Miami Herald / Associated Press

The former manager of a peanut processing plant in Georgia that was linked to a deadly salmonella outbreak five years ago pleaded guilty Wednesday to seven criminal counts, including fraud.

Samuel Lightsey was the manager of Peanut Corporation of America's plant in Blakely, Georgia, when an outbreak of salmonella traced to the company's peanuts killed nine people and sickened hundreds in 2009. Lightsey and three others were later charged with scheming to manufacture and ship tainted peanuts.

Lightsey faces a possible fine of up to $250,000 and maximum prison terms of one to 20 years on each of the seven charges. Prosecutors recommended in a plea agreement that Lightsey serve no more than six years in prison. He will be sentenced at a later date.

Also charged in the case are Peanut Corporation owner Stewart Parnell, his food broker brother Michael Parnell, and Georgia plant quality assurance manager Mary Wilkerson.

The salmonella outbreak caused one of the largest recalls in history and prompted the government to file criminal charges, rarely pursued in food poisoning cases because intentional contamination is hard to prove.

The company's dirty processing plants were blamed for the outbreak that killed nine people and sickened hundreds. One plant was in Plainview, Texas, which the State Department of Health Services closed Feb. 10, 2009, after product samples tested positive for salmonella.

Food and Drug Administration inspectors found bad conditions inside the processing plant in Blakely, including mold, roaches and a leaky roof. According to email uncovered by congressional investigators shortly after the outbreak, Parnell, who invoked the Fifth Amendment to avoid testifying before Congress in February 2009, once directed employees to "turn them loose" after samples of peanuts had tested positive for salmonella and were then cleared in another test.

The indictment unsealed in February 2013 says the company misled its customers about the existence of salmonella in its product, even when lab tests showed it was present. It says the co-workers even fabricated certificates accompanying some of the peanut shipments saying they were safe when tests said otherwise.

The company later went bankrupt.

The 76-count indictment charges the Parnell brothers and Lightsey with conspiracy, mail fraud, wire fraud and the introduction of adulterated and misbranded food into interstate commerce with the intent to defraud or mislead. Stewart Parnell, Lightsey and Wilkerson were also charged with obstruction of justice.