(ALBUQUERQUE, N.M., AP) — A federal appeals court on Monday temporarily halted plans by companies in New Mexico and Missouri to begin slaughtering horses, continuing on-again, off-again efforts to resume domestic equine slaughter two years after Congress lifted a ban on the practice.

The 10th U.S. Circuit Court of Appeals in Denver issued a temporary injunction barring the Department of Agriculture from inspecting the plants, which were gearing up to open in the coming days after a federal judge in Albuquerque on Friday dismissed a lawsuit by The Humane Society of the United States. The Humane Society and other animal protection groups alleged the department failed to conduct proper environmental studies when it issued permits to the slaughterhouses.

The Humane Society filed an immediate appeal and won an emergency injunction.

“Horse slaughter is a predatory, inhumane business, and we are pleased to win another round in the courts to block killing of these animals on American soil for export to Italy and Japan,” said Wayne Pacelle, president and CEO of The Humane Society of the United States. “Meanwhile, we are redoubling our efforts in Congress to secure a permanent ban on the slaughter of our horses throughout North America.”

Blair Dunn, who represents Valley Meat Co. of Roswell, N.M., and Rains Natural Meats of Gallatin, Mo., emphasized the order was temporary.

“We know the 10th Circuit will follow the law and allow my clients to proceed as soon as our side is considered,” Dunn said. “The plaintiffs have misstated the law, the facts and the science. We look forward to a quick decision when the facts are considered and the District Court’s careful decision is reviewed.”

Valley Meat Co. owner Rick De Los Santos has been fighting for two years for approval to open. He converted his small, struggling cattle slaughterhouse in southern New Mexico to take advantage of a shift in Congress that lifted a ban on funding for inspections at horse slaughterhouses.

A vote to end that funding in 2006 had effectively banned horse slaughter until the money was restored in 2011.

The USDA, however, did not approve the first permits for horse slaughter plants until this summer. But just days before Valley Meat and a third company, Responsible Transportation of Sigourney, Iowa, were set to open, U.S. District Judge Christina Armijo issued a temporary restraining order that kept the plants closed until she decided the lawsuit by the animal protection groups. Responsible Transportation since has converted its plant to cattle.

The debate over a return to domestic horse slaughter has been an emotional one that centers on whether horses are livestock or companion animals and what is the most humane way to deal with the country’s horse overpopulation, particularly in the drought-stricken West. Supporters say it is better to slaughter unwanted horses in regulated domestic plants than to ship them thousands of miles to sometimes inhumane plants in Mexico.

During the two-year fight, De Los Santos and his wife have received numerous death threats. And last summer, there was a suspicious fire at the plant.

The issue has divided horse rescue and animal welfare groups, ranchers, politicians and Indian tribes.

The companies want to ship horse meat to countries where it is consumed by humans or used as animal feed.