Soil samples collected at Rocky Flats near a spot with a previously elevated plutonium reading have tested within safe margins.
The Denver Post reports state health officials requested tests on new samples from the periphery of the Rocky Flats National Wildlife Refuge to ensure they were within safe levels.
The wildlife refuge is on the buffer zone around a plant that manufactured plutonium triggers for nuclear weapons.
Officials say an August soil test from a different part of the buffer zone yielded a plutonium reading five times higher than the government-defined standard. In September, the U.S. Fish and Wildlife Service released test results from within the refuge showing samples were well below risk levels.
Officials say the latest samples were each tested twice using different methods to detect the radionuclide.