Despite years of online allegations that one of the most popular dog food brands has been poisoning pets, it wasn’t until just weeks ago that the cat was let out of the bag in a court filing. A class action lawsuit was filed that blames the deaths of thousands of dogs on one of Purina’s most popular brands of chow.

Googling Nestle Purina Petcare’s Beneful brand will get you the pet food manufacturer’s website, a Facebook page with over a million likes, and, in stark contrast, a Consumer Affairs page with 708 one-star ratings supported with page after grim page detailing dogs suffering slow, agonizing deaths from mysterious causes.

Internal bleeding. Diarrhea. Seizures. Liver malfunction. It reads like something from a horror movie or a plague documentary, but a suit brought in California federal court by plaintiff Frank Lucido alleges that this is all too real—and too frequent to be a coincidence.

But it all relies upon finding a chemical that may be in the food—and has been a staple in dog food recalls in the past—with an experiment that neither Lucido, his lawyers, or even independent scientists have even begun to conduct.

Lucido said it began last month when his beloved German shepherd began losing an alarming amount of hair, smelled strange, and wound up at the vet with symptoms “consistent with poisoning.” A week later, his wife found one of their other dogs, an English Bulldog, dead. An autopsy showed signs of internal bleeding in the stomach and lesions on the liver, symptoms eerily similar to the shepherd’s, according to the complaint. Then their third dog also became ill.

“All these dogs are eating Beneful,” explained Jeff Cereghino, one of the attorneys representing Lucido in the action. “And the dogs are all, for a variety of reasons, not in the same house. So you take away the automatic assumption that the neighbor didn’t like the dogs or whatever. He was feeding them Beneful at the start of this, and one got sick and died, the other two were very ill. And then he started doing a little research, and he realized the causal link, at least in his mind, was the food.”

It doesn’t take much digging to uncover what appears to be a pattern of allegations, Cereghino said. Lots and lots of allegations. After hearing Lucido’s story, Cereghino checked it out for himself.

“We found a significant number of folks who were trying to draw exactly the same causal link. Thousands,” he said.

The sheer volume is what made the seasoned lawyer—one who said “a good part of our business is class action work”—realize something may be fishy.

“If it’s a hundred or so, it’s like, ‘Okay, a lot of dogs eat Beneful; things happen.’ But when you start getting into the thousands… The long and short of it is the complaint pyramid is such that even with the Internet–easy access to complain about things– there’s still a very large percentage of folks who simply don’t complain, or whose vet tells ‘em, ‘We don’t know what happened,’ and they’re not drawing conclusions or leaping to assumptions, “ he said.

“But when I look at 4,000? Holy hell, there’s a lot of people out here.”

So Cereghino and his partners started talking to those people, comparing more and more of the stories of heartbreak.

“There seems to be somewhat of a singular event. [The dogs] are vomiting. They’re having liver problems, failures,” he said. “I’m not a vet, but you look at some of this stuff and say, ‘OK, we’re starting to have similar symptoms across the board, and we’re starting to have causation.’”

When these dire accusations first started appearing online years ago, the initial accusation was that one of the additives in the food, propylene glycol, was the culprit.

Purina maintains the type of propylene it uses is perfectly safe for consumption, saying on its website: “Propylene glycol is an FDA-approved food additive that’s also in human foods like salad dressing and cake mix.”

It’s also the same substance that caused the spiced whiskey Fireball to be recalled in Europe, which found excessive amounts of the chemical, also used in antifreeze, in the cinnamon swill last fall. The tainted liquor was from the North American batch because, in the U.S., much higher volumes of antifreeze additives are OK for human—or canine—consumption.

“It’s horrible. That is something that you don’t want in dog food,” noted veterinarian and author Karen "Doc" Halliga n when reached by phone. “It’s controversial. Why do you want to take a risk if there’s any kind of chance that that could be bad for them?”

But whether it’s good for dogs or not, food grade propylene glycol has been approved by the Food and Drug Administration. It also hasn’t been linked to toxicity, especially the type being alleged against Beneful.

Cereghino thinks there’s another culprit in the mix, and he’s named it in the lawsuit. They’re called mycotoxins.

Translated directly from the Greek words for “fungus poison,” mycotoxins are, essentially, a toxic byproduct of mold. When it comes to ducking discovery, they’re an especially crafty brand mold byproduct, and one found in all types of grains. In fact, a new study, released this month, indicates they’re even pretty common in breakfast cereal.

Related: The Toxin Hiding in Your Cereal

If you read the ingredients label of Beneful, it sounds an awful lot like breakfast cereal: ground yellow corn, corn gluten meal, whole wheat flour, rice flour, soy flour. Sure, there’s some “chicken byproduct meal” and “animal fat preserved with mixed-tocopherols,” but the food is certainly more grain than meat.

“In the channels of trade, grain is quite a lot like hamburger these days. As in ‘There’s multiple cows in a hamburger,’ if you will,” explained Dr. Gregory Möller, professor of environmental chemistry and toxicology at the University of Idaho and Washington State University joint School of Food Science. “It’s a mixed and blended commodity. So one farmer, one granary, or one mill, may have not stored their product well, which allowed for mold growth in storage.”

Even if a scientist were to stumble upon a load of grain rife with mycotoxins, Möller added, he or she could test it and still miss them.

“You can go into a sample that is known contaminated,” Möller noted. “But the particular sub sample you pull may not have enough on it to actually see. There is that challenge.”

This can be exacerbated when the host grain is earmarked for non-human use.

“Commodities that are targeted towards pet foods are managed a little bit differently, in terms of the regulatory criteria they have to pass,” he continued. “It is a very large industry. There is attention and concern about quality, but there is a difference in how the concern is managed.”

In layman’s terms?

“I think what’s put forth here is a plausible scenario,” Möller said.

When asked about the alleged symptoms described in the class action suit and online, especially the repeated liver failure, Halligan was clear in her potential diagnosis, especially as it pertained to animals of a variety of ages.

“Toxins would be real high on my list. If an animal ingests some type of toxin, that can lead to liver disease because the liver has to process it,” said Halligan.

But there have not yet been any tests to determine if mycotoxins are in Beneful at all—or any other dog food, for that matter.

Cereghino said he’s determined to find that out.

“As soon as we are able to, and the federal courts move at a fairly rapid rate, we will get discovery,” said Cereghino.

That’s when Cereghino will get to find out where Beneful’s products come from, how they’re stored, whether there’s a “connecting piece in the storage or the grain, the sourcing of it all, that sort of make sense.” He plans on running tests on the food both he and other members of the class action suit have saved to send over to a lab in the next few weeks.

That’s when they’ll know if those potentially dangerous chemicals are in the formula. And, if they are, they’ll still have to fight to prove that the mycotoxins are dangerous enough to make thousands of dogs sick.

As for Purina, when approached for comment, Keith Schopp, vice president of corporate public relations, read this statement to The Daily Beast:

“We believe the lawsuit is without merit and we intend to vigorously defend ourselves. Beneful is a high-quality nutritious food enjoyed by millions of dogs each year and there are no product quality issues with Beneful.”