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Pet food giant Purina launched a national campaign in support of its Beneful brand last week — just as an ongoing lawsuit against the brand expanded its allegations that the popular feed is making dogs sick.

The amended complaint against Nestlé Purina PetCare Company’s Beneful dry kibble dog food was filed on June 8 in California federal court, adding 26 additional pet owners from states spanning coast to coast.

The lawsuit now alleges that Beneful contains toxins and that Purina has been offering cash settlements in exchange for silence from those who voice complaints about the brand.

The amendments to the suit come on the heels of a national campaign launched by Purina last week defending its products. The “I Stand Behind Beneful” campaign features a full-page advertisement in the New York Times and a TV commercial showing workers who both make Beneful and feed it to their own pets, the company said.

“This really boils down to the fact that we’re really proud of the Beneful product and there are no issues with the quality,” Keith Schopp, vice president of corporate relations for Purina, told NBC News. “We thought one of the best ways to show that pride would be actually through the men and women who make Beneful and feed it to their own pets.”

An ad for Purina Beneful appearing in The New York Times on June 14. Purina

The company featured a second full-page in the New York Times on Sunday after the initial launch this week.

Plaintiff and pet owner Frank Lucido, who claims one of his dogs died and two others became ill after eating Beneful, initiated the original lawsuit against Purina in early February of this year.

Jeffrey B. Cereghino, the lawyer spearheading the case against Purina, said he and the law firms participating in the suit have been contacted by thousands of people who believe Beneful may have poisoned their dogs.

“The immediacy of folks willing to participate was really quite extraordinary,” he said.

The amended suit includes 26 additional plaintiffs with similar stories and claims that Purina failed to disclose that the brand contains substances toxic to animals — including Industrial Grade Glycols (IGG), lead, arsenic and mycotoxins. The suit is seeking class-action status and $5,000,000 in damages.

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Purina has continued to deny the allegations in the suit, publishing an extensive statement on its website on June 9 in response to the amended complaint.

“We’re really disturbed by the ongoing false and unsubstantiated allegations,” Schopp told NBC News.

The company said in the statement that Beneful is not formulated with IGG, but rather “high-quality human food-grade levels” of propylene glycol.

While Industrial Grade Glycols are not approved for use in food by the FDA, food-grade propylene glycol is approved as safe for use in human and dog food. The original lawsuit listed propylene glycol in its complaint, instead of IGG.

The Purina statement also says the company tests “for well over 150 substances,” including mycotoxins, lead and arsenic as part of its food safety and ingredient surveillance programs.

Dr. Kurt Venator, director of veterinary strategy and programs at Purina, said the strict testing standards extend to their ingredient suppliers as well.

Purina products “meet or exceed food quality and safety standards,” he said.

The pets listed in the lawsuit vary in age and in length of time consuming Beneful before becoming ill, but the consistent symptoms, according to the suit, include: vomiting, diarrhea, loss of appetite, liver or kidney malfunction and failure, seizures, and even death.

Plaintiff Rob Benham, of Versailles, Indiana, told NBC News he and his family believe Beneful is responsible for the death of Sadie, a 7-year-old Miniature Fox terrier, and the ailing health of their 5-year-old Shih Tzu Willie.

Willie, top, a 5-year-old Shih Tzu, suffered liver and kidney problems and is still recovering. The Benhams believe switching his diet to Beneful is to blame. Sadie, below, a 7-year-old Miniature Fox Terrier, died in Oct. 2013 within four months of switching her diet to Beneful. Rob Benham

Benham, 47, began feeding his dogs Beneful in June 2013, partially for financial reasons, he said.

“Purina is a household word, we felt very safe in doing that,” he said.

Within a month, Sadie began losing weight dramatically, Benham said. When they took her to their veterinarian, they were informed Sadie had developed problems with her liver and would need medication. But the vet was unable to find the cause of the problem.

“He was baffled,” Benham said. “He could think of no reason for it.”

The symptoms only got worse.

“She started having trouble with her vision and was staggering everywhere,” he said. “She had always been very healthy.”

“On October 19 of 2013, we lost her,” Benham said through tears.

Cereghino said there was a disconnect between the company’s new campaign and how Purina has treated concerned customers.

The amended suit claims that Purina has been contacting consumers who post negative experiences with Beneful to social media, denying liability while offering them cash settlements in exchange for restrictive confidentiality agreements. The lawsuit claims to include a copy of a non-disclosure agreement for a complaint involving Beneful.

Schopp, the Purina spokesman, said any customer service agreements and compensation were “good-will gestures” by the company and a common practice in many industries.

“Anytime consumers have questions they can contact us, whether validated or not we have at times responded to them and offered compensation as a good-will gesture,” he said. “The notion that this is something we just started or there is some sort of a negative motive here is nonsense.”

The dry kibble variations named in the suit include Purina Beneful Healthy Weight, Purina Beneful Original, Purina Beneful Incredibites, and Purina Beneful Healthy Growth For Puppies, Purina Beneful Healthy Smile, Purina Beneful Healthy Fiesta, Purina Beneful Healthy Radiance, and Purina Beneful Playful Life.