(CNN) The U.S. Food and Drug Administration is warning dog owners of a possible link between certain dog food brands and a serious form of canine heart disease.

The FDA has investigated more than 500 cases of dilated cardiomyopathy (DCM) in dogs eating certain types of food, according to their statement.

DCM is a condition that effects a dog's heart and results in an enlarged muscle. Dogs with DCM tire easily, cough, and have difficulty breathing.

FDA identifies 16 dog food brands

When the FDA first alerted the public in 2018 to cases of DCM, the agency didn't mention specific brands; only foods labeled as "grain-free" and containing peas, lentils, other legume seeds and/or potatoes as the main ingredients.

As part of that investigation, the FDA has now identified 16 brands of dog food which had the most frequent reported cases of DCM. The top three brands, according to the FDA, are Acana, named in 67 reports; Zignature, named in 64, and Taste of the Wild, named in 53 reports.

Dog Food Brands Named Most Frequently in DCM Cases Reported to FDA

"We know it can be devastating to suddenly learn that your previously healthy pet has a potentially life-threatening disease like DCM. That's why the FDA is committed to continuing our collaborative scientific investigation into the possible link between DCM and certain pet foods," said Dr. Steven M. Solomon, director of the FDA's Center for Veterinary Medicine.

Solomon says the FDA has not determined the nature of the potential link. but it encouraged dog owners to work closely with their veterinarians.

FDA is providing an update on its ongoing investigation into reports of dilated cardiomyopathy (DCM) in dogs eating certain diets. @FDAanimalhealth is sharing new data, updated stats, & a compilation of adverse reports of DCM submitted to FDA: https://t.co/0ZlqfoPGPf pic.twitter.com/UvVSQRj1wy — U.S. FDA (@US_FDA) June 27, 2019

Agency findings are inconclusive

The agency has not asked the companies to recall their products. "We have shared case report information with these firms so they can make informed decisions about the marketing and formulation of their products," the FDA wrote.

"In parallel with the FDA investigation, our own third party internal studies found no link between our high quality pet food products and any of the other physical characteristics that correlate to DCM," says Zignature in a statement posted on their website.

Zignature added, "as we continue to have great confidence in our naturally sourced diets that meet the needs of dogs who suffer from allergies and grain intolerances, we are providing an exclusive line designed by our expert formulation team that is nutritionally sound and grain-inclusive."

Champion Petfoods, the parent company for Arcana , said it takes the issue and is working "internally and with other industry leaders on research into the cause of DCM in order to help Pet Lovers understand the facts," Champion said in a written statement.

"...Of the 77 million dogs in the U.S., 0.5% to 1% have DCM, and of those dogs with DCM, fewer than 0.1% are speculated to have DCM related to diet, although that is not scientifically proven. In the recipes Champion makes, we emphasize fresh and raw meat with total animal-derived ingredients ranging from 60 to 85 percent of the finished product. Legumes are not a significant feature in Champion's recipes, and never have been. "

CNN has reached out to Taste of the Wild, but has not received a response. The company addressed the investigation in 2018, saying "scientists have been unable to pinpoint the exact cause of DCM."

What you can do

If DCM is caught early, heart function may improve in cases that are not linked to genetics with appropriate veterinary treatment and dietary modification, according to the FDA.

If a dog is showing possible signs of DCM or other heart conditions, the FDA encourages you to contact your veterinarian as soon as possible. In extreme cases such as sudden weakness or collapse, you may need to seek emergency veterinary care.

The FDA says it will continue to investigate the connection and will update the public as information becomes available.