(CNN) Are we safe? That's the concern that's been in the back of neighbors' minds when they look at the looming Portsmouth Gaseous Diffusion Plant in Pike County, Ohio, Jennifer Chandler said.

"It looks like they make clouds there," the Piketon village councilwoman thought as a child, seeing steam coming out of the stacks. "When I was growing up, I didn't have any idea what they did."

The US Department of Energy plant was built to produce enriched uranium for the nation's nuclear weapons program during the Cold War and, in later years, supported commercial nuclear reactors. One of three such plants in the United States, it operated from 1954 to 2001, when it commenced decontamination and decommissioning, which continues today.

In the past five years, five students in the nearby Scioto Valley Local School District have been diagnosed with cancer; three of them have died, Chandler said. Her cousin, Luke, who grew up near the facility, died years ago of leukemia. She wonders whether it is a cancer cluster.

"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. It's a sensitive subject: "This isn't a game, you know. These are people's lives."

On Monday, Zahn's Corner Middle School in Piketon was closed because enriched uranium had been detected inside the building and neptunium-237 had been detected by an air monitor next to it.

"As the crow flies, the school is less than two miles from the DOE property boundary," Chandler said.

The district said Tuesday that the school will remain closed "until the source, extent, level of contamination, and potential impacts to public health and the environment can be determined."

Enriched uranium, which is engineered from uranium ore to help build nuclear weapons, and neptunium, a byproduct of this process, are both radioactive and considered "contaminants of concern" -- they increase a person's risk of developing cancer -- by the Department of Energy.

Piketon, an Appalachian village of 2,146 people, is located along the Scioto River in south Ohio. The middle school serves more than 300 students and includes 25 staff.

"There's just not a playbook when dealing with this, and we're kind of writing the script as we go," School District Superintendent Todd Burkitt told CNN affiliate WLWT in Cincinnati.

Decontamination and decommissioning

Background given by a senior Department of Energy official indicates that routine air samples in the area of the Portsmouth Plant revealed only trace amounts of the two radioactive contaminants, both of which were more than 1,000 to 10,000 times below the established threshold of public health concern. The agency emphasized that it takes all detections seriously, "even those that are at such low levels."

The agency issued its annual site environmental report in March, and that's when the public and the school district learned of the radioactive contamination, Chandler said. She added that sampling was done in 2017.

"They issued the 2017 data to the community two years later," she said. Later, it was found that in 2018, the air monitors had picked up americium, another radioactive byproduct of nuclear production.

Chandler's neighbor Elizabeth Lamerson lives within the 2-mile immediate notification area -- If there's an accident at the plant, she will be given instructions on what to do, Chandler explained.

Lamerson started asking "lots of questions," including about what air emissions look like, and when she didn't get any answers from the Department of Energy, she took matters into her own hands and started a sample collection process in conjunction with scientists from Northern Arizona University, Chandler said.

The university conducted a "public interest study" to investigate potential sources of uranium and other contaminants in environmental samples from the vicinity of Piketon. The report attributes a "possible source" of some of the contamination to the construction area.

In 2015, the Department of Energy and the Ohio Environmental Protection Agency agreed on a plan for disposing more than 2 million cubic yards of waste that would be generated from the plant's decontamination and decommissioning process. This plan included construction of an on-site waste disposal facility.

Construction activities, including site clearing and roadway construction, began around 2017, and that's when the monitors detected contamination, Chandler said.

Based on documentation provided by the Department of Energy, Matthew Brewster, health commissioner of the Pike County General Health District, believes that contamination "reached the air monitoring station as a likely result of activities related to the construction of the waste disposal facility."

Environmental samples

that included water samples taken in 2009 stated that uranium-238 had been detected below levels determined to be acceptable levels by the DOE, yet cadmium, chromium, and lead were detected "above [the Portsmouth Plant] groundwater Preliminary Remediation Goals," which are set to protect health during cleanup projects. Before construction, a Department of Energy report that included water samples taken in 2009 stated that uranium-238 had been detected below levels determined to be acceptable levels by the DOE, yet cadmium, chromium, and lead were detected "above [the Portsmouth Plant] groundwater Preliminary Remediation Goals," which are set to protect health during cleanup projects.

The Northern Arizona University scientists working with the community published their own technical memorandum on April 27 that included sample results taken within a 5-mile radius of the nuclear plant. The report found enriched uranium inside Zahn's Corner Middle School. It also detected neptunium in water and sediment samples from a private property adjacent to the construction site and enriched uranium, neptunium and plutonium on private properties and streams and creeks within the Piketon vicinity.

This report, combined with the Department of Energy's annual survey, prompted the school district to close the middle school.

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Both the school district and the Pike County Health Department urged the agency to stop construction on the disposal facility at the plant.

However, US Assistant Secretary of Energy Anne White, who discussed next steps with the health district on Friday before the school closing, said that until the agency has better data, it would not stop construction work.

She said the agency wants to sponsor a third-party assessment to examine all of the contamination issues mentioned in the Northern Arizona University report, which would include sampling at the school, on private properties and of state air, water and soil.

Brewster said the local health department and other state authorities can decide on both the scope of the assessment and the independent contractor. He expects that the contractor will be decided this week and test results should be returned 30 days after environmental sampling.

Chandler said the top priority for the health district is that "concerns are alleviated."

"At some point, we have to trust the scientists who are doing these calculations and coming back to us and saying, 'yes, this building is completely safe' or 'no, we've got an issue,' " she said.

The community is "100% supportive" of the Department of Energy getting the site cleaned up, she said, but contamination has been released into the atmosphere and depositions of uranium have been found not only in the school but in attic dust of local houses.

"If there's things being released into the air from construction activities, stirring up fugitive dust that's now being blown off-site and hitting air monitors, [the agency needs] to look at that and figure out a way to do these activities without contaminating the community," Chandler said.