Contaminated feed is being blamed for the recent deaths of dozens of horses at an Oklahoma ranch known for breeding generations of award-winning rodeo livestock.

Feed manufacturer Livestock Nutrition Center claimed responsibility for the deaths on Saturday, saying that “a failed cleanup procedure and a sensor malfunction” likely caused a contamination of monensin ― an antibiotic toxic to horses ― in the feed delivered to Beutler and Son Rodeo Company in Elk City.

Ronnie Castlebury, the president of the feed company, called it an isolated incident and said “no other feed has been impacted.”

“Words are cheap but we are dedicated to assist and support the Beutler family and make this right because our customers and employees expect and deserve it,” Castlebury said.

The Oklahoma Department of Agriculture, Food and Forestry confirmed to HuffPost on Wednesday that its investigation into the matter, which involves the Kansas Department of Agriculture and the U.S. Food and Drug Administration, remains ongoing.

A spokesperson said ODAFF is awaiting the results of tests conducted on feed samples taken from the ranch last week. It has not received any calls, complaints or messages related to the feed from other customers since the investigation began.

The department had previously said it was investigating the deaths and analyzing a feed sample using two state-certified laboratories after being contacted by a veterinarian about the illnesses on Aug. 23.

The Kansas Department of Agriculture told HuffPost last week that it was reviewing the feed company’s records, as well as its labeling procedures and operating procedures, “to ensure that the appropriate protocols for feed are being followed.” A spokesperson for that department did not immediately respond to a request for comment Wednesday.

Initial reports suggested that monensin, also known by the brand name Rumensin, could be to blame. The drug is used as a feed ingredient for livestock like cattle, sheep, goats and chickens, but it is toxic to horses and domestic animals.