BAY SHORE - Residents in Bay Shore say their home values have plummeted because they're living on top of an underground toxic plume.

Resident Bill Sullivan and 37 others in his area have filed a lawsuit against National Grid, alleging their property values have been ruined by toxic groundwater. Long Island's former electric company, LILCO, had a fuel processing plant in Bay Shore decades ago that left potentially cancer-causing chemicals in the groundwater.

National Grid and the state Department of Environmental Conservation (DEC) have been cleaning up the site and testing the water for more than five years. Residents say neither National Grid nor the DEC will provide documentation that the area is safe.

"We believe the cleanup requirement efforts have been successful in preserving the health and well-being of our neighbors in the Bay Shore community," National Grid said in a statement.

When asked why they haven't shown residents anything in writing, a company spokesman said she couldn't comment.

The DEC did not return calls for comment.