The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) are teaming up to investigate over 1,000 dog deaths and three people who fell ill after consuming  chicken, duck and sweet potato pet jerky imported from China. Following the FDA’s last update back on October 22, 2013, 4,800 complaints of illness, some including multiple pets in one household, have been reported to the agency involving 5,600 dogs, 24 cats and three people.

According to the FDA’s latest report, around 60 percent of the cases were tied to gastrointestinal and liver disease, 30 percent kidney or urinary disease, and 10 percent that included neurologic, dermatologic, and immunologic symptoms. Approximately, 15 percent of kidney and urinary cases also tested positive for Fanconi syndrome, a rare kidney disease tied to reported cases of pet and human illnesses. The FDA has still been unable to identify an exact cause for the sudden outbreak.

The FDA and CDC are collaborating on a study tracking food consumed by sick dogs reported to the agency compared to what healthy dogs ate. Researchers hope the analysis will be able to tell what type of food (human or pet food) is making pets and people sick. The FDA has already performed 26 post mortem examinations on 26 dogs reported to the agency since October 2013. It was discovered that 13 of these dogs had consumed pet jerky and 11 showed signs of kidney disease while two were identified with gastrointestinal disease.

“The agency continues to review case records, test treat samples from reported cases, screen tissue, blood, urinary and fecal samples, and communicate with the attending veterinarians and pet owners to thoroughly investigate select cases,” the FDA said in a statement. “Because of the volume of information received in response to the Dear Veterinarian letter, the agency has not completed an update to our online case spreadsheets. FDA plans to complete and post these updates in the coming months.”

Of the three humans who fell ill as a result of consuming pet jerky, two were toddlers who ingested it accidently and one adult who was snacking on the pet treat for unknown reasons, NBC News reported. One of the toddlers was diagnosed with a salmonella infection and the other suffered from a gastrointestinal illness and fever, similar to the symptoms experienced by dogs in the same household. The adult reportedly suffered from symptoms including nausea and headache.

“Testing of jerky pet treats from China has also revealed the presence of the drug amantadine in some samples containing chicken,” the FDA added. “These samples were from jerky pet treats that were sold a year or more ago. Amantadine is an antiviral that is FDA-approved for use in people. It has also been used in an extra-label manner (using an approved drug in a way that isn’t listed on the label) in dogs for pain control, but FDA prohibited its use in poultry in 2006.”