OKLAHOMA CITY (AP) -- A nearly century-old Oklahoma company that supplies stock for rodeos had as many as 70 horses die a week ago after receiving what an owner believes was tainted feed.

Rhett Beutler, co-owner of Beutler and Son Rodeo Co. near Elk City, told KFOR-TV that the horses died shortly after being fed.

"We didn't know what was going on, we just got the feed and started feeding it like always," Beutler said. "Then all of a sudden looked up and there was horses just falling over, dying."

Beutler and Son officials did not immediately return messages seeking comment Friday.

"All them horses are kind of like my kids; I've raised them from time they were born," Beutler told KOKH-TV, "Once you lose one, that's one too many."

The Oklahoma Department of Agriculture, Food and Forestry said in a statement that it was notified Aug. 23 of the horses' deaths related to a bulk order of feed and has opened an investigation.

"An inspector visited the Beutler and Son site on behalf of the department on Monday, August 26, and learned that the feed originated in Kansas," according to the statement. "The ODAFF inspector collected a feed sample which is being analyzed in two state-certified laboratories."

The department said it is working with the Kansas Department of Agriculture to investigate the company that provided the feed.

"We have initiated an investigation which includes labeling procedures, operating procedures and a review of their records to ensure the appropriate protocols were followed" in producing and shipping the feed to Oklahoma, said Kansas agriculture spokesperson Jamie Stewart.

The company that provided the feed has not been identified because of the ongoing investigation, Stewart said.

Dr. Gregg VeneKlasen, of the Timber Creek Veterinary Hospital, the Beutlers' veterinarian, declined to comment on the deaths other than to call it a "tragedy."

Beutler and Son was founded in 1929 as Beutler Brothers near Elk City, about 105 miles (169 kilometers) west of Oklahoma City, and provides stock for rodeos, including the National Finals Rodeo.

The company is providing the majority of stock for the Elk City Rodeo starting Friday night, according to Elk City Rodeo board member Randy Hargis, who said the events include bareback horse riding, saddle bronc riding, bull riding and steer wrestling.