JoNel Aleccia of NBC News writes that two of the top-selling brands of jerky treats for pets will soon return to U.S. store shelves, a year after a nationwide recall and with government experts no closer to solving the mystery that has linked the products to hundreds of animal deaths and thousands of illnesses.

Nestle Purina Pet Care officials say they’ll reintroduce a line of Waggin’ Train treats for dogs starting next month, including products made from a single supplier in China and new products sourced entirely in the United States.

“We’ve worked hard to put in place the highest quality controls in the dog treat industry,” Waggin’ Train President Nina Leigh says in a promotional video.

And Del Monte Foods Corp. officials said they’ll resume selling Milo’s Kitchen Chicken Jerky Strips and Chicken Grillers Recipe treats in March using U.S.-sourced meat.

Federal Food and Drug Administration officials told NBC News they know about Nestle Purina’s plans and have reviewed them, but they said the company doesn’t need special permission, known as pre-market approval, to reintroduce the treats. And they said they couldn’t discuss the review.

That’s despite repeated FDA warnings that consumers should avoid jerky pet treats after the agency received reports that since 2007, nearly 600 pets, mostly dogs, have died and 4,500 have been sickened after eating chicken, duck and sweet potato products made in China. That figure is up by 900 reports since October.

The move drew immediate criticism from veterinarians, pet owners and animal advocates, who said it wasn’t clear exactly what changes, if any, the companies made to the products, and that they were worried their return to market would only sicken more pets.

Florida veterinarian Sofia Morales, who has treated at least three cases of Fanconi syndrome, a serious illness linked to the treats, said she would want to see results of clinical trials in pets showing that the revamped products were safe.

“Right now, what I’m recommending to people is not to feed jerky,” she said.

Jerky makers have consistently said there is no proven link between their products and the pet poisonings. FDA officials have not demanded recalls because they have no proof of contamination.

Nestle Purina officials said they have made “significant enhancements” to the Waggin’ Train production process, including limiting meat sourcing to single suppliers and requiring that each batch of treats be tested for a range of contaminants, including salmonella, melamine, di-ethylene glycol and antibiotics, as well as heavy metals, pesticides and mycotoxins, or molds.

It’s like marketing microbial food safety: the best companies will abandon the soundbites and provide actual data, in this case verification data, that their products are safe. Until then, it’s just marketing BS.