Rewarding your favorite canine with a tasty treat may pose health risks. The Food and Drug Administration released updated information on Friday about an ongoing investigation into illnesses and deaths caused by jerky pet treats imported from China.

As of May 1, 2014 the regulatory agency has received more than 4,800 reports of illness affecting a total of 5,600 dogs, 24 cats, and 3 people. A number of reports came from owners with multiple dogs. More than 1,000 dogs have died. There have been 1,800 new cases of illness since the last FDA report in October 2013.

The FDA says the jerky treats were almost all manufactured in China, with flavors that include chicken, duck and sweet potato.

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Among the reports, 60 percent of the animals were said to suffer from gastrointestinal and liver disease; 30 percent had kidney and urinary disease; and 10 percent of complaints filed involved various other symptoms including dermatological, neurological and immune system-related problems. Approximately 15 percent of cases involving urinary or kidney problems tested positive for Fanconi syndrome, an uncommon kidney disease.

General symptoms of illness include decreased appetite, decreased activity, vomiting, diarrhea with blood or mucous, increased water drinking, and increased urination within hours of eating the treats.

The FDA has obtained a number of well-documented case reports from veterinarians who treated animals that were sickened with the treats. The agency also conducted postmortem examinations on 26 dogs, and found clues that the treats may have been linked to the cause of death in at least half of the animals.

In several analyzes, the snacks were found to contain low levels of antibiotics as well as the drug amantadine, an antiviral and antiparkinsonian medication. However, the FDA does not believe the illness was caused by amantadine because symptoms in the case reports are not typically associated with the drug. Chinese manufacturers have told federal agencies they will perform additional testing of their products, while the FDA has notified U.S. companies that the jerky pet treats tested positive for several drugs.

Since 2007, the FDA has struggled to make progress in the investigation of reportedly tainted dog treats. In the fall of 2013, the agency issued letters to veterinary clinics throughout the country asking them to inform pet owners about illness associated with the treats. But there have been many challenges along the way in the investigation. For one, symptoms of illness tend to be inconsistent from an animal to animal. Additionally, many pet owners often fail to take their sick dog to the vet right away and instead choose to monitor symptoms for a few days.

The FDA says it has called upon the expertise of the Centers for Disease Control to to conduct further studies and research.