RENO, Nev. (AP) — The U.S. government can proceed with plans to sell more than 400 mustangs gathered at a national wildlife refuge to a private contractor that critics say has a history of reselling them for slaughter, a federal judge ruled Friday.

U.S. District Judge Miranda Du refused to grant an emergency order blocking the sale because she said theU.S. Fish and Wildlife Service has tightened restrictions on the Mississippi contractor, which has been unable to account for the current whereabouts of more than half of the 262 horses it has purchased from the agency since 2010.

However, Du said she’ll give horse advocates another chance next week to prove why the horses from the Sheldon National Wildlife Refuge on the Nevada-Oregon line are of historical and cultural significance and deserve the same protection as those managed by the Bureau of Land Management.

She also set a hearing for Oct. 10 for advocates to argue why they think their First Amendment rights have been violated by restrictions the Fish and Wildlife Service has placed on public access to the holding facility where the animals have been stored since being rounded up earlier this month.

Du said advocates can file a new brief Monday, but she won’t in the meantime prevent the agency from moving forward with next week’s planned shipment of horses to contractors, including J&S Associates of Pelahatchie, Miss.

“The government can start that process,” Du said, adding that she believes agency officials have screened potential adopters and “have made reasonable efforts to prevent horses from going to slaughter.”

The Fish and Wildlife Service initiated a formal investigation of J&S Associates last year based on a complaint from one of the plaintiffs in the current case, California horse advocate Bonnie Kohleriter. But officials said the agency could not document any evidence horses were knowingly transferred to others for slaughter.

“There’s simply no evidence any horses have gone to slaughter,” Justice Department lawyerTravis Annatoyn told Du on Friday.

Gordon Cowan, a lawyer representing Kohleriter and Laura Leigh of the Nevada-based advocacy group Wild Horse Education, said the agency doesn’t know what happened to more than half of the animals.

“The bulk of them disappeared. The (government) would admit today they don’t know where they are,” Cowan said. “They have nothing in writing, horses are missing and they are about to repeat the process.”

The agency concluded that 112 of the 262 horses J&S received from 2010-12 were placed with “suitable and appropriate adopters.” But it acknowledged the disposition of 82 animals placed with one adopter was uncertain, with at least some of those horses being sold by the adopter.

J&S did not provide documentation for the disposition of 65 horses, but it appeared they were being held on pastures owned by two private individuals in Mississippi. Agency lawyers said J&S may not have kept records adequate to show the location of these horses.

The review concluded the original terms of the contract didn’t require horse adoption contractors to provide detailed disposition information, only a list of the adopters, they said. New rules require additional screening of prospective adopters and reporting of complete horse disposition data, including contact information for all adopters.

Stan Palmer of J&S Associates said Friday he thinks the new reporting requirements will discourage some people from adopting horses. He said he doesn’t believe any of the horses he has purchased ended up at slaughter houses.

“To my knowledge, that hasn’t happened,” he said. “There have been people who have taken horses with the expressed purpose of training them and selling them.”

Palmer noted that the contract did not call for any information on the people who got the horses from him and he provided only what was required to ensure the privacy of the purchasers.

“The advocacy groups have gotten so bad at harassing and haranguing these people. I was trying to avoid them having to go through that if it wasn’t necessary,” he said.