PIKETON (AP) — State health officials and the U.S. Department of Energy say dust samples taken in late May from a southern Ohio school near a former uranium enrichment plant showed no radioactivity beyond naturally occurring levels.

Scioto Valley Local School District had closed the Zahn’s Corner Middle School in Piketon in mid-May after traces of radioactive material were discovered.

But the Department of Energy tells The Columbus Dispatch there is no public health risk from radioactive material at the school.

A university scientist who found some of the earlier traces questioned the department’s testing methodology, which the DOE defends.