DETROIT – Federal animal health officials are still trying to solve the mystery source behind hundreds of pet deaths linked to chicken jerky treats made in China.
To date, 600 pets have died and more than 3,600 animals have become sick since the problem began.
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An initial warning on pet treats was sent out by the Food and Drug Administration in 2007, consumer complaints about pet deaths were back on the rise in 2011.
More: FDA warns of dangerous dog treat.
One hundred new pet deaths --linked to jerky treats--have been reported to the FDA since January of 2013, according to NBC.
The FDA has yet to pinpoint a source causing the deaths, but symptoms reported range from gastrointestinal illnesses to kidney failure.
Two of the largest sellers of pet jerky treats issued a voluntarily recall of product as a precaution in January.
Nestle Purina PetCare Company recalled Waggin' Train and Canyon Creek Ranch brand dog treats and Milo's Kitchen --owned by the Del Monte Corp. of San Francisco -- voluntarily recalled their Chicken Jerky and Chicken Grillers home-style dog treats nationwide, says NBCNews.com.
Three other retailers have also recalled jerky treats for the same issue.
The FDA has yet to issue an official recall of any pet jerky treats despite pressure from consumers and families who have lost pets.