Upgrade costs and the loss of production demonstrate the huge risks manufacturers are exposed to once the safety of their food is compromised.

The plant has been closed since February 14, after the US Centers for Disease Control and Prevention (CDC) linked about 600 cases of foodbourne illness across 47 states to consumption of Peter Pan and Great Value peanut butter products manufactured at the facility.

Works completed at the plant in Sylvester, Georgia, include roof repairs, new equipment installations and creating new processes to better separate raw materials and the finished product, according to reports in the Associated Press.

ConAgra said it had traced the contamination back to three incidents that took place in August 2006.

The contamination was most likely caused by moisture from a leaking roof and a faulty sprinkler system, which mixed with salmonella present in raw peanuts and dust at the plant.

The plant was cleaned thoroughly after the incidents, but the salmonella remained and came into peanut butter prior to packaging.

While the recall alone cost ConAgra a reported $66m, the company still faces lawsuits in several states.

Once production is underway, ConAgra Foods will begin shipping Peter Pan Peanut Butter to retailers this summer.