COLUMBUS (AP) — Companies involved in work at a former uranium enrichment plant in Ohio say a federal court should dismiss a lawsuit alleging nearby residents were unknowingly exposed to radioactive contaminants that spread to other properties.

Several residents sued the companies over contamination from the site of the former Portsmouth Gaseous Diffusion Plant in Piketon and construction of a waste-disposal facility there. They seek damages and medical monitoring, and class-action status to represent nearby residents and students at a school where radioactive material was found.

In a filing this week, defendants argued the case should be dismissed because the claims weren’t brought under a federal law governing liability-related matters for nuclear facilities. Those defendants include cleanup contractors and the company that ran a uranium enrichment project at the site in recent years.