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.