PIKETON, Ohio (CBS Local) — An Ohio middle school is shut down indefinitely because of concerns of radioactive contamination from a nearby shuttered uranium enrichment plant, officials said.

Zahn’s Corner Middle School in Piketon will be closed at least for the remainder of the school year, Scioto Valley Local School District officials announced Monday.

The public school, which enrolls about 360 students, will be shut down until “the source, extent, level of contamination and potential impacts to public health and the environment can be determined,” according to the district.

In a letter to parents, the school board said enriched uranium had been detected inside the building and neptunium-237 had been detected by an air monitor next to it. Both are highly carcinogenic radioactive chemicals, which authorities believe stemmed from the activity at the nearby Portsmouth Gaseous Diffusion Plant.

The plant made nuclear materials for the U.S. Department of Energy from 1954 to 2001, the agency said. Contractors are building a waste disposal site on the plant as they work to clean up the 3,000–acre facility.

The DOE confirmed that trace amounts of neptunium were found in two ambient air monitoring stations near the Portsmouth plant but decided not stop construction work at the disposal site until it had better data.

“Even though the detected levels were well below the established thresholds of concern for public health, DOE is taking immediate steps to obtain independent soil and air quality samples in the surrounding area, and will take all appropriate actions to address community concerns,” the agency said in a statement.

Five students in the nearby Scioto Valley Local School District have been diagnosed with cancer; three of them have died, Jennifer Chandler, a Piketon village councilwoman, told CNN. Her cousin, Luke, who grew up near the facility, died years ago of leukemia.

“You don’t want to make a claim that you can’t back up. How is this caused? Is this a genetic cancer? Is this an environmental cancer? I’m not a medical professional,” she said. “This isn’t a game, you know. These are people’s lives.”