HOUSTON -

Mothers call it liquid gold; and these days new moms who can't produce enough of their own breast milk are turning to Craigslist to get it.  But now a new study confirms buying breast milk from a complete stranger online can be risky.

A year ago, we showed you how Houston area women were buying and selling breast milk on Craigslist. Now there is a warning from researchers. Results of new tests show samples found on public milk-sharing websites were contaminated with dangerous bacteria.

Northwest Houston mom Nicole says after the birth of her third child, she noticed she wasn't producing as much breast milk.

"It's really difficult when you find out your body is not efficient enough to feed your child," she told Local 2. 

She looked into certified milk banks, but the costs add up.  Frustrated, she posted a heartfelt ad on Craigslist. It read "If you could find it in your heart to donate anything... even a onetime donation will help so much."

Rina Rahman, a nurse and new mom had a surplus supply. She saw Nicole's ad online. After discussing things like diet, lifestyle and recent blood work, the two women met up.

But exchanges like these do come with a warning. Nationwide Children's Hospital in Ohio examined samples of breast milk purchased over the internet and found troubling results.

"Staphylococcus bacteria, streptococcus bacteria, coliform bacteria, that would include bacteria like E. coli," said Dr. Sarah Keim of Nationwide.

Out of 101 samples purchased online, three-quarters were contaminated with potentially dangerous bacteria.

"Many of the samples had very very high levels of bacterial contamination," said Dr. Keim.

Nancy Hurst is director of the Mother's Milk Bank at Texas Children's Pavilion for Women. The donor breast milk there is pasteurized to minimize bacteria and donors are screened.

"We're asking them about medication they're on, any foreign travel certain types of illnesses," said Hurst.  "Then they do a blood test on them as well and check that so you don't see that with the sharing or selling of the milk online."

The FDA and American Academy of Pediatrics recommend against casual milk sharing citing the risk of exposure to infectious diseases such as HIV or hepatitis.