But after seven years of investigating, the Food and Drug Administration (FDA) still does not know what is tainting the jerky treats that have been linked to thousands of pet illness complaints, it said on Friday.
The snacks, mostly made in China, have been sold by many different companies under various brands, NBC News reported.
There is no one product responsible for all of the complaints.
The three humans affected are two toddlers who accidentally ate the snacks and one adult who may have been munching on them, the FDA said.
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In animals, about 60 per cent of the treat complaints report gastrointestinal or liver disease, and another 30 per cent of complaints are about kidney and urinary disease, WTSP, a CBS-affiliated television station in Tampa, Florida, reported.
The remaining 10 per cent are about various other symptoms, including neurological and skin conditions.
Luke Qin, the owner of a factory in Shandong, China, even ate a duck jerky treat to prove his business's snacks are harmless, NBC reported.
"Human standard. You can try eating," he said.
Meanwhile, The FDA is teaming up with the Center for Disease Control to further investigate.
"It's quite sad when you see it dawn on the people that they're trying to reward their best buddy there and then now they're the ones who have been making them ill," Brett Levitzke, a New York veterinarian, told NBC.