JACKSONVILLE, Fla. -- The Environmental Protection Agency is now investigating a product called Hartz Advanced Flea and Ticks Drops.

CORRECTION A previous version of this story erroniously reported on an EPA internal memo. The EPA has not recommended that Hartz Flea and Tick Drops For Cats 10 Pounds and Under be removed from sale. The EPA is only investigating the safety of the product, and says that the product complies with and is labeled to comply with all applicable federal and state regulations.

Although it's sold in many grocery stores, some cat owners say the product causes loss of appetite, and possibly forces the animal into debilitating seizures.

A veterinarian told Channel 4 that the product should never have been allowed on the market.

A cat name Kirby is unable to walk and can hardly stand. Her vet said she twitches from a seizure caused by toxic poisoning.

They're the same symptoms afflicting Lady -- a 2-year-old Burmese.

Morgan says Lady was perfectly healthy until he says he applied Hartz Advanced Flea and Tick drops for cats 10 pounds and under on Lady's back.

He says within hours his cat was nearly dead.

"She was practically in a comatose state," owner Chris Morgan said. "She had no energy, no enthusiasm. She wouldn't walk, she wouldn't eat."

"This is a condition we see in many, many cats that have had over-the-counter topical flea preparations applied to them," Andrew Lawless told Channel 4 investigator Jennifer Waugh.

Lawless says blood tests reveal Lady's liver shows signs of toxicity -- the same problem Kirby's vet says caused this cat to have a seizure.

Both vets say this can be caused by an insecticide -- called Phenothrin. Phenothrin is the primary ingredient -- 85 percent -- of Hartz Advanced Flea and Tick Drops for Cats.

The drops are sold in most grocery stores to pet owners looking for a less expensive solution to flea control.

Kirby and Lady's owners both told Channel 4 they bought and used the product on their pets.

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The Eyewitness News investigators called 30 local veterinarians, learning that 19 them -- more than 60 percent -- reported seeing seen cases where cats have either died or become very sick after being treated with Hartz Advanced Flea and Tick Drops for Cats.

The Environmental Protection Agency said it approved Hartz Advanced Flea and Tick Drops for sale in stores nearly two years ago.

Morgan said that Hartz asked for asked him for more information about Lady, then said that there is no proof that its drops made Lady sick.

And they are right. Lady's vet says it is possible that Lady had some type of pre-existing condition that no one knew about. But he also said Lady only became sick after she was treated with the drops.

An attorney representing one woman who says these drops also made her cats sick is seeking to file a class action lawsuit on her behalf.

So far, he says more than 350 pet owners have joined the suit.

While an internal EPA memo recommending that the product be reevaluated for its safety was written months ago, the product is still on grocery shelves.

Hartz told Channel 4 they stand behind their product. Its company vice prsident told Jennifer Waugh that they believe their product is sound.

"I think the key here, Jennifer, is that the information you are citing is preliminary. It is an interim report," Dr. Albert Ahn of Hartz Mountain said. " Based on the information we have and based on a review of all the data that we have, we stand firmly behind these products."