In the growing online market for breast milk, more than one in 10 tested samples contained cow's milk, researchers reported Monday. Nearly all of the adulterated samples carried enough bovine DNA to reveal they'd been mixed before shipping with at least 10 percent cow's milk. Some selling moms use that method to covertly amplify their supply, which typically fetches $1 to $2 per ounce. The findings illustrate the underlying profit motives that compels some women to peddle their breast milk, often referred to as "liquid gold," on web exchanges. What's worse: The contamination could harm babies with dairy intolerance, especially preemies, doctors say. The FDA recommends against feeding babies breast milk acquired through the Internet because it unlikely to have been properly screened for infectious diseases like HIV or chemical contaminants such as illegal drugs. The Human Milk Banking Association of North America has a list of non-profit milk bank locations on its website.