Tom's of Maine toothpaste was manufactured with water containing bacteria, while a "black mold-like substance" was found in a factory where the product was made, according to a warning letter from the U.S. Food and Drug Administration.

The November 5 letter stated that Tom's Simply White Clean Mint toothpaste contained Pseudomonas aeruginosa, a germ that can cause infections in the blood and lungs, the FDA letter said.

Colgate-Palmolive, which owns Tom's of Maine, didn't immediately respond to a request for comment.

The FDA letter also flagged another bacteria, Ralstonia insidiosa, which was found in water sources at the factory. Another product, Wicked Cool! Anticavity Toothpaste, was found to include another type of bacteria, Paracoccus yeei, the letter stated.