RENO, Nev. - Wild horses rounded up on federal land in the West and sold to a private owner have been slaughtered for the first time since a new law went into effect, a government official told The Associated Press on Thursday. The U.S. Bureau of Land Management in Washington D.C. is "looking into" the circumstances surrounding this month's sale of six wild horses to an Oklahoma man and their subsequent slaughter at a commercial packing plant in Illinois, said agency spokeswoman Celia Boddington. "This is something we regret," she added. Cavel International in DeKalb is the only horse-slaughter and commercial-packing plant in Illinois. In December, Congress repealed the 34-year-old ban on slaughtering wild horses that run free across the West. The move has brought a backlash from activists who want to reinstate full protection for the mustangs. Boddington said the BLM is implementing the new law in such a way as to require promises from buyers that they will provide long-term care for the horses. However, the language is not legally binding and buyers that choose to immediately turn around and sell the horses for slaughter can do so. In the case of the six horses sold this month, "The owner did provide us with assurances that he would provide long-term care for these animals," Boddington said. The Humane Society of the United States objected Thursday to the recent slaughter of the wild horses. They were sold for slaughter on April 18 to Cavel, said Nancy Perry, the Humane Society's vice president for government affairs. "The BLM says they prescreen the buyers but obviously that isn't working," she said. Cavel General Manager Jim Tucker said the slaughterhouse has legally purchased wild horses from sellers who have the appropriate certification from the BLM. "BLM allows horses to be adopted and held for a certain amount of time and allows them to be slaughtered," he said. He confirmed that within the last week, Cavel purchased and slaughtered some horses from a seller who had gotten them through the BLM. He declined to say how many horses were purchased or from whom they were purchased, saying that such information is "proprietary." He also said it wasn't the first time the slaughterhouse has processed wild horses. Boddington said it has been legal since the 1970s for people who take ownership of wild horses under a separate BLM horse-adoption program to eventually sell them for slaughter. Last year, Illinois' legislature rejected a bill that would have banned the slaughter of horses for human consumption in the state. The failed measure was aimed at keeping the Cavel slaughterhouse from reopening, more than two years after the building was destroyed by fire. Before the fire, the Belgium-based Cavel slaughtered 15,000 horses a year at its DeKalb plant. The meat was shipped to Europe for human consumption and most of the rest of the animal was sent to rendering plants to be processed for other uses, such as fertilizers and glue. The new federal law, written by Sen. Conrad Burns, R-Mont., was passed at the urging of ranchers concerned about overpopulation of the horses and their effect on the range. "I'm sorry to see these animals destroyed," Burns said. "The man who purchased these horses from the BLM lied and said they were for a church youth group. He then turned around and sold them to a slaughterhouse. I continue to believe the program is working, as nearly 2,000 horses now have new homes and people to care for them, but it's a shame that six didn't make it." BLM has sold and delivered nearly 1,000 horses since the law was passed. Some 950 more have been sold and are awaiting delivery. "This is the first time we're aware" any have been sold for slaughter, Boddington said. Daily Chronicle City Editor Chris Rickert contributed to this report.