Despite persistent safety fears and numerous unanswered questions, two major pet food manufacturers will bring their jerky treats back to store shelves in February and March.

NBC News reported that Nestle Purina Pet Care will reintroduce its Waggin' Train treats in February, and Del Monte Foods Corp. will bring back Milo's Kitchen Chicken Jerky Strips and Chicken Grillers recipe treats in March.

The two food manufacturers voluntarily withdrew their jerky products from the markets after low levels of unapproved antibiotics were found, but all tests have reportedly failed to demonstrate a definitive link between the treats and pet deaths and illnesses, the FDA has said.

Nestle Purina Pet Care said it will be reintroducing products made from a single supplier in China, as well as new products sourced entirely in the U.S., NBC reported. In addition, the company will reportedly require that every batch of treats be tested for various contaminants such as salmonella, melamine, di-ethylene glycol, and antibiotics, as well as heavy metals, pesticides, and mycotoxins.

Even though the companies say they have taken rigorous precautions to ensure the treats are safe for pets, the reappearance of the treats has raised the ire of veterinarians, pet owners, and animal advocates who wonder if the manufacturers have truly distanced themselves enough from the mysterious problem affecting pets, NBC reported.

"We need to raise hell! Too many unanswered questions," said New York pet owner Robin Pierre, who told the media that her 2-year-old pug Bella had died after eating chicken jerky treats. "Was it the antibiotics? What did they find? We want to know. They have said nothing other than they enhanced their product. What has changed?"

FDA still wants veterinarians to help with the investigation

The FDA's investigation into the jerky treat-related illnesses is ongoing, and veterinarians can continue to help the agency by submitting specific samples and information as outlined in last year's FDA letter to veterinarians.