Texas-based Blue Bell Creameries, which stopped production and distribution of ice cream to 25 states in April after the discovery of listeria, said on Friday that it has identified areas in plants where the bacteria may be present.

The company did not specify in a statement in which of its three facilities listeria may be present but said that none was found in any of its ice cream.

"In our facilities, we have identified suspected areas where bacteria may be present but in no case have we confirmed listeria monocytogenes," the company said in a statement.

"The entire purpose of our enhanced environmental testing is to identify locations where bacteria could be found in our facility in order to properly clean and sanitize the surface and prevent contamination," the company added. It said that testing was taking place at all three plants.

Blue Bell, ranked the No. 1 ice cream brand in the country in 2014, recalled all products last spring after 10 reported cases of listeria in four states were linked to Blue Bell frozen treats. Three of the people sickened, all hospital patients in Kansas, later died.

The disease, caused by eating food contaminated with listeria, primarily affects older adults, pregnant women, newborns and adults with weakened immune systems, according to the U.S. Centers for Disease Control and Prevention.

Blue Bell suspended production at its plants in Brenham, Texas; Broken Arrow, Oklahoma, and Sylacauga, Alabama last spring and said it conducted a major overhaul of production at all three plants.

Blue Bell laid off or furloughed hundreds of employees as a result of the shutdown.

Starting in November, the company began a phased process of returning its ice cream to store shelves. The company said the next phase of the process, in which ice cream will be distributed in Tennessee, Kentucky, the Carolinas, and Virginia, will proceed as planned.

