MINNEAPOLIS (AP) -- Plainview Milk Products Cooperative has voluntarily recalled its instant nonfat dried milk and whey protein as well as some thickening agents due to potential salmonella contamination.

The products, which were not directly sold to consumers, were made over the past two years. The thickening agents include fruit stabilizers and gums.

There have been no reported illnesses, Plainview said late Monday.

Food and Drug Administration and Agriculture Department testing of the Plainview, Minn., company's products has not found salmonella contamination, but General Manager Dallas Moe said in a statement that contamination had been found when the products were blended with other ingredients outside of its facility. A dairy shake powder made by one of Plainview's customers was found to contain salmonella.

Before the recall, the FDA's environmental testing found some positive test results for salmonella at the company's Plainview plant. The testing included taking swab samples from walls, ceilings, floors and equipment.

Plainview said it is getting all equipment in question disassembled and cleaned and using anti-microbial surface coatings as a further preventative measure.

Salmonella can cause serious infections, especially in children, the elderly and those with weakened immune systems.

Several recent food recalls have been related to bacterial contamination, including a salmonella outbreak last winter traced to a peanut company that sickened more than 600 people and that was blamed for at least nine deaths. A separate outbreak of salmonella last year linked to jalapeno peppers from Mexico led 1,400 people to become ill.