MENLO PARK (CBS SF) — An analysis of hamburger meat sold in stores and restaurants in Northern California found some samples with traces of human and rat DNA, along with some substituted ingredients or others not found on the label.

Menlo Park-based Clear Labs took a look at more than 250 hamburger products, including ground meat, frozen patties, fast food burgers and veggie burgers. The ground meat included beef, chicken, turkey, pork and others.

READ MORE: VIDEO: Wind-Whipped Dixie Fire Ignites Homes In Greenville; Fire Crews 'Going Into Life Threat Mode'

The analysis found contamination, hygenic or substitution problems in 13.8 percent of the products sampled from dozens of brands and retailers. Examples would be meats observed in molecular analysis but not shown on the label, absence of ingredients advertised on the label, or trace amounts of DNA from humans, insects or rats.

Clear Labs said incidents of human or rat contamination were a small fraction of the samples and are not likely to be harmful for human health. Of the human DNA, Clear Labs said in the report, “The most likely cause is hair, skin, or fingernail that was accidentally mixed in during the manufacturing process.”

The firm also noted that the U.S. Food and Drug Administration says certain low levels of food contamination are acceptable.

READ MORE: Photos: Dixie Fire Destroys Homes, Businesses In Greenville

Vegetarian products fared worse than than overall sample study. 23.6 percent of veggie products showed some form of label discrepancy or quality issue, including a black bean burger that had no black beans in it at all.

Despite the findings, researchers said the study suggests “the beef industry as a whole has benefited from stringent regulation and aggressive testing requirements.”

The full report can be found on the Clear Labs website.

 

MORE NEWS: How To Help Victims Of Dixie Fire

Carlos E. Castañeda is Senior Editor, News & Social Media for CBS San Francisco and a San Francisco native. You can follow him on Twitter or send him an email.