RENO -- Citing safety concerns and environmental hazards, federal managers said Wednesday they are banning access to all the public lands that make up nearly half of a large, polluted copper mine in Northern Nevada.

The Bureau of Land Management's closure order is the most sweeping U.S. action to date restricting access to the former Anaconda mine covering about 5 square miles bordering Yerington.

It will remain in place while Atlantic Richfield Co. assesses the extent of contamination under a new cleanup order from the U.S. Environmental Protection Agency, BLM said.

"Until testing is completed and hazards are removed it is necessary to close the entire site to public use," BLM site manager Craig Smith said.

Recent tests show unusually high levels of uranium in the soils in the area where chemicals were used to process the copper for decades.

"There are also physical hazards around the mine site that make it potentially dangerous for the general public," Smith said.

BLM is responsible for site security of the 1,492 acres of federal land at the site, Smith said. Trespassers are subject to fines up to $1,000 and a year in prison.

Jim Sickles, the EPA's manager of the site, said earlier this year the property should be secured "so we don't have people wandering around the site where there might be radiological contamination."

The mine, about 60 miles southeast of Reno, produced copper for about 30 years until 1978.

Atlantic Richfield, a former owner of the mine site, is responsible for the cleanup because the most recent owner, Arimetco of Tucson, Ariz., filed for bankruptcy in 1997 and abandoned the site in 2000.

The new closure does not apply to authorized employees or contractors, BLM said.