On Tuesday, the FDA asked pet owners and veterinarians to contact them if their dog or cat has become ill after eating jerky pet treats — packaged snacks made of chicken, duck, sweet potatoes or dried fruit.

At least 3,600 dogs and 10 cats have become ill after eating jerky treats since 2007, according to the FDA. Of those cases, 580 have involved the death of a pet.

While the agency has issued a number of consumer alerts as a result, and has initiated investigations that have taken scientists to jerky treat manufacturers in China, they have yet to determine the exact cause of the illnesses.

"This is one of the most elusive and mysterious outbreaks we've encountered," read a prepared statement from Bernadette Dunham, director of the FDA's Center for Veterinary Medicine. "Our beloved four-legged companions deserve our best effort, and we are giving it."

In a "Dear Veterinarian" letter issued Tuesday, FDA officials told veterinarians that they may request samples of urine or tissues from affected animals and provided instructions on how to report cases to the administration.

In those cases in which pets have become ill, symptoms appeared within hours of eating the treats, officials said. Symptoms have included decreased appetite, decreased activity, vomiting, diarrhea — sometimes with blood or mucous — increased water consumption and increased urination.

The most severe cases have involved kidney failure and bleeding of the stomach or intestines. Some pets have collapsed or suffered convulsions, officials said.

"The agency urges pet owners to be cautious about providing jerky treats," an FDA bulletin warned. "If you do provide them and your pet becomes sick, stop the treats immediately, consider seeing your veterinarian, and save any remaining treats and the packaging for possible testing."

Since the treats are not part of a fully balanced diet, officials said they can be discontinued without harm.

Instructions for reporting suspected jerky treat illnesses are contained in this FDA fact sheet.

Most of the implicated jerky treats have been manufactured in China, and the FDA said it has been in contact with regulators there.

To date, scientists have tested more than 1,200 jerky treat samples in search of chemical and microbiological contaminants. They have yet to find a specific cause of illness however.

When several brands of jerky snacks were removed from store shelves in January of this year, following an investigation by the New York State Department of Agriculture and Marketing, reports of illnesses dropped.

The New York investigation identified low levels of antibiotic residues in the treat packaging. While the FDA said it is unlikely the antibiotics were the cause of the illnesses, scientists are investigating the possibility that low levels of the medication could trigger sickness if consumed over a long period of time, the FDA said.