Another brand of horse feed is suspected in the death of three horses on an equestrian farm in South Carolina. Despite testing that showed the feed to be contaminated with a deadly additive, ADM Alliance Nutrition has yet to issue a recall and the feed that likely killed them remains on the shelf.

The deadly feed  — ADM Alliance 12% Pellets [Patriot 12% Supreme Performance Horse Feeds] — believed to have killed the horses last month at Camelot Farms Equestrian Center tested positive for monensin oxide, a supplement used in cattle feed that is poisonous to horses.

Despite testing at the Diagnostic Center for Population and Animal Health at Michigan State University that came back positive for monensin, ADM says they are still “investigating these allegations”and claim they “have not received any other reports or complaints about monensin in our horse feed.”

Camelot Farms owners believe the tainted feed came from 70 bags they purchased in late November from G&G Feed & Seed in Beaufort. Incredibly, the deadly feed was still for sale at the store and it even a small amount of monensin can permanently weaken a horses heart. No word yet on how many other retail locations in the U.S. that also might be selling the deadly feed.

Mark Kennedy, the farm owner, said he fed 45 of 48 horses with the tainted feed for two-and-a-half weeks. Another horse is seriously ill and will likely be euthanized and more are likely to become ill and die as the weeks go by, even though the Kennedys say that so far no other horse at the farm are is currently exhibiting any symptoms.

Since the deaths, the South Carolina Department of Agriculture took samples of the feed and said the agency plans “to test for another deadly toxin, mycotoxin” instead. Apparently, the agency doesn’t have the equipment to test for monensin.

The U.S. Food and Drug Administration (FDA) is also involved in the investigation and despite having the legal authority to issue a Class I recall based on the deadly nature of the contaminated feed, one has not been issued. All the FDA would say is they are aware of the situation “and looking into it.”

ADM Alliance representatives also visited the farm before Christmas to collect samples, but have declined to share the test results with the Kennedys or the public.

The Camelot Farms deaths are similar to another recent Florida case of contaminated feed and dying horses. Since October, six horses have died at Masterpiece Equestrian Center in Florida and another 16 are sick and most of them are expected to die. The deaths are blamed on feed tainted with the same supplement, monensin.

Recently, the farm settled with the feed manufacturer, Lakeland Animal Nutrition. Unlike ADM, the Lakeland company recalled their contaminated horse feed, and stopped production of equine feed all together.

ADM will likely face a costly settlement, because when the Kennedys noticed the parallels in the Lakeland Animal Nutrition case, they called the attorney for the Masterpiece Equestrian Center to discuss their next step.