Two people are being investigated for one of the worst cases of alleged horse neglect the Surrey SPCA says it has ever seen.

A barn with five starving horses was found by investigators after the collapse of another horse in a ditch in Langley.

The animal was forced to try and pull a car from the ditch, where it had become stuck. A video shows it had collapsed after the effort of pulling the car and failing to get up again after struggling. It was put down at the scene.

Witness Barbara Feitl said the horse was in obvious distress.

"It's heartbreaking. I can't imagine how someone can do this," she said. "They were at first trying with four or five people to pull and push and the horse kept falling back. It was obvious it was extremely exhausted."

Feitl said it was wrong to misuse animals that were so dependent on human care.

"They are just like children they trust us depend on you take care of them and feed them and then there are people out there -- you can't even call them humans -- to do this to an animal."

When the SPCA visited the Surrey barn that was home to the dead animal, they found five other horses, all thin and weak, with their bones protruding.

"We were in the process of going in there with a warrant -- as a result we received a call to help with a horse in the ditch," said Eileen Dreever, SPCA cruelty investigator.

Dreever ended up in tears when she saw the five remaining horses.

The SPCA is recommending charges be laid against the owners.

Dreever is looking for farms to foster the five remaining horses. If you can help, call her at 604-709-4670.

With a report from CTV British Columbia's Shannon Paterson.