A spokeswoman for the company told FoodProductionDaily.com that she could not confirm the source for the bacteria at the facility in Burlington, Wisconsin.
Nestle said a sample of the chocolate morsels had tested positive for salmonella a few weeks ago. The firm had not been forced to issue a recall as the product was never distributed for sale.
The plant had subsequently undergone an intensive cleaning after the positive result but disruption to production had been minimal, confirmed the spokeswoman.
"We have rigorous quality assurance protocols and procedures in place, which include testing of product during our manufacturing process," Nestle’s Laurie MacDonald told the Milwaukee Journal Sentinel. "As part of our extensive quality procedures, we also tested product manufactured before and after this single positive sample, and all product tested negative. Quality is our number one priority and this is example of our extensive procedures at work."
Last month, Nestle informed the US Food and Drug Administration (FDA) that it detected E.coli 0157 H7 in its Toll House refrigerated cookie dough. Again the firm said it had not been necessary to issue a recall as none of the tainted dough had left the site in Danville, Virginia.
This was the second occasion that E.coli had been found at the plant. In summer 2009, Nestle issued a nationwide recall of it Toll House dough after the bacteria was found in dough samples. The company confirmed it had implemented new testing protocols at the facility had begun using heat-treated flour in the manufacture of the dough.