About 140 malnourished horses and 200 head of cattle have been seized from a property just outside Drumheller, Alta., officials say.

The horses were very thin and in poor condition, said Terra Johnston, the executive director of the Alberta Society for the Prevention of Cruelty to Animals.

About 12 cows and horses were found dead at the scene, RCMP said.

Three or four horses had to be euthanized because they were too sick to be transported, RCMP said in a release.

"We were concerned about the ongoing care. Certainly we had a veterinarian assist us, and her recommendation was that we seize the horses and remove them to a care taking facility. They need to get some care," Johnson told CBC News.

Alberta SPCA officials executed a search warrant at the property on April 18, acting on a tip from the public, Johnson said.

The animals were difficult to capture because they are essentially wild, she added.

Officers with the RCMP Livestock Unit and Drumheller RCMP were still at the East Coulee property on Thursday, along with SPCA officials.

A full investigation needs to take place before any charges are considered, Johnson said.

SPCA officials have had dealings with one of the people associated with the property in the past, she added.

Drumheller is about 110 kilometres northeast of Calgary.