Jerky dog treats made in China have been linked to about 1,000 dog deaths and illness in three people, but after years of investigation, the Food and Drug Administration doesn't know what is tainting the treats.

The treats, which are mostly made in China and are sold under a variety of brand names, have sickened 5,600 dogs and 24 cats.

Three people — two toddlers and one adult — have also reported gastrointestinal and kidney problems after consuming the jerky treats.

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