The Swiss firm - with its US headquarters in Glenvale, California - said the St Louis closures were "strictly a production issue" and that the consolidation will bring both Illinois plants up to maximum production capacity.
The bulk of production will be moved to existing Nestle plants in Bloomington and Itasca, Illonois, while about 40 percent of production will be moved to a Nestle plant in Saltio, Mexico.
According to LA DailyNews.com, Barb Skoog, Nestle spokeswoman, assured that overall US production would not be affected.
The 383 employees at the St. Louis plants were notified of the impending closures Thursday.
They were told in a letter, said a report on STLToday.com, that the decision to close the plants resulted from "the industry's intensely competitive environment".