SEARSPORT (AP) – The deaths of seven horses last month were the result of tainted food, not animal cruelty, officials concluded.

Tests performed on the dead horses’ manure sent to the University of Wisconsin have validated the presence of monensin, an anti-bacterial additive in cattle feed that’s deadly if eaten by horses, said Dr. Don Hoenig, the state veterinarian.

“Right from the start, the local veterinarian was not concerned that this was an animal cruelty issue,” Hoenig said. “Monensin fits the clinical pictures and points out this was not a cruelty case.”

After the seven horses died, the remaining seven horses were removed from Kathy Hecht’s home and taken to Lynn Boynton’s Goose River Farm in Swanville. Three more horses have died but four remain at the farm, Boynton said.

A necropsy of one of the dead horses conducted by a pathologist at the University of Maine in Orono failed to determine the cause of death.

Hoenig said he did not know how the horses got the tainted feed at Hecht’s farm in Searsport. Testing of Hecht’s commercial horse feed revealed no contamination and no traces of monensin, Hoenig said.

Hecht, who could not be reached for comment, reportedly brought 35 horses from North Dakota in 2004 and almost immediately caught the attention of animal welfare agents. Many people jumped to conclusions when the horses died last month.

Hoenig said there were some problems with Hecht’s horses. “They were not perfect, but they were not emaciated. They had food, water and shelter, and she was cooperative. This didn’t reach the threshold for seizure.”