Four horses, including three thoroughbreds, were found neglected and emaciated this week in Northwest Miami-Dade County’s C9 Basin, an area notorious for the illegal slaughter and selling of horse meat.

“There were tires, toxic waste and four horses,” said Richard Couto, an animal rights activist who investigates illegal horse slaughter. “The horses were feeding off of whatever they could feed on.”

The animals – three thoroughbreds and one American quarter horse – were found Wednesday near Northwest 178th Street and 134th Avenue, in a field that looked like a dumping area, said Couto, whose organization is called Animal Recovery Mission

Couto said he immediately called police and the South Florida Society for the Prevention of Cruelty to Animals.

Miami-Dade police confirmed Thursday that they responded to the area in response to a report of skinny horses.

“There was no indication that the horses were going to be slaughtered,” detective Edna Del Castillo said in a statement.

Couto disagreed. “This a was pre-slaughter holding site for horses,” he said.

The South Florida SPCA found a fifth horse, also a thoroughbred, Wednesday in Southwest Miami-Dade County. Couto said he believed that horse had been abandoned but did not appear to be awaiting slaughter.

By Thursday, the four thoroughbreds were being nurse back to health in Southwest Ranches with help of Florida Trac, a South Florida-based retirement and placement program for horses that competed at either Calder Race Course or Gulfstream Park.

The quarter horse was with the SPCA.

“These horses are so skinny,” Couto said, “that just giving them a regular meal will kill them.”

Racehorses have unique tracking numbers tattooed on their lips. Using those numbers, Couto already had names and ages for two of them Thursday. One was Cornish Gold, a 12-year-old, gray-colored mare, he said. Another was El Tabrany, a 6-year-old, bay-colored gelding.

“Bad people get ahold of these horses, and they have relationships with the illegal slaughter farms in Miami-Dade,’’ Couto said. “They give these horses to these slaughter houses as a favor or for a small payment, maybe a couple hundred bucks.”

This isn’t the first time abandoned horses have turned up in the Basin, possibly in line to be slaughtered. The illegal activities in the Basin reached the point that, in January 2010, federal, state and county inspectors swept through there to stop the rampant illegal butchery, hazardous waste dumping and brutal handling of animals that had gone on, sometimes openly, for years.

During that summer, county employees pushed deep into the Basin, trying to bring properties up to code and, in the process, push out illegal activities.

Less than a year later after the sweeps, in August 2010, police found a former racehorse, Magic Express in the Basin, close to starvation.

Couto said the raids made a difference. But horses like those found this week give him reason to fear the illegal slaughter farms are trying to return.

“The raids did a lot of good. We shut down 70 illegal slaughter farms,” Couto said. “But some have reopened.