More than 1,000 dog deaths may now be linked to toxic jerky treats, according to a recent update from the Food and Drug Administration (FDA).

The agency said that since 2007, there have been almost 5,000 complaints of pet illnesses related to the treats. The majority of the symptoms reported include gastrointestinal or liver disease, and about a third were linked to kidney and urinary disease.

About 10 percent of the illnesses included other signs such as neurologic, dermatologic, and immunologic symptoms, and about 15 percent of the kidney and urinary disease cases also tested positive for Fanconi syndrome – a rare kidney disease also associated with the pet deaths.

The FDA is still unsure of the specific cause for the reported illnesses and deaths, but most cases reportedly occurred after the pets had eaten chicken, duck or sweet potato jerky treats imported from China. No specific brands were recalled in the FDA's latest release, but Dr. Jonathan Levine, an associate veterinarian at Blue Pearl Veterinary Partners in New York City, said owners should always check the labels of whatever foods they give their pets.

“Always be aware of what you're buying and where it's coming from,” Levine said.

Yet that may not always be enough to keep pets safe; products stamped “Made in the USA” could still contain ingredients sourced from China or other countries, the FDA warned.

In 2007, some pet food companies voluntarily removed some jerky treats from the market. But, at the time, the FDA said it didn't want to issue a recall without a definitive cause. Those products included Milo's Kitchen Chicken Jerky Treats and Chicken Grillers, made by Del Monte, and Waggin' Train and Canyon Creek Ranch dog treats, made by Nestle Purina.

The FDA has partnered with the Centers for Disease Control and Prevention (CDC) to figure out what foods may be contributing to pet disease. The study will compare the foods eaten by sick dogs to those eaten by dogs who haven’t gotten sick, in order to determine if the jerky is really the culprit.

So far, testing of jerky pet treats from China revealed low levels of antibiotics as well as the antiviral drug amantadine in some chicken samples. Although FDA-approved for pain-control applications in humans and in dogs, the agency prohibited its use in poultry in 2006 to help preserve its effectiveness.

The FDA does not believe amantadine contributed to the illnesses, as the side effects of the drug do not correlate with the symptoms seen in the pets; however, amantadine should not be present at all in jerky treats.

Chinese authorities have agreed to conduct additional screenings and follow up with jerky treat manufacturers, and the FDA has notified U.S. treat makers of the presence of amantadine in some jerky products. The agency will also continue testing these products for drugs and other antivirals.

The FDA cautioned pet owners that jerky pet treats are not required for a balanced diet. If your pet experiences any sign of illness, including vomiting, diarrhea and lethargy, contact your veterinarian right away.

Click for more from My Fox NY.

Click for more from the FDA.