A former poultry health laboratory site off U.S. 113 in Millsboro has been tagged as the likely source of a toxic chemical that tainted Millsboro's drinking-water supply last year, a state official said Thursday.

Cleanup of the contamination could cost "several million" dollars, according to Kathleen Stiller-Banning, a program manager for Delaware's Department of Natural Resources and Environmental Control.

High pollution levels in town wells prompted health officials in October to warn against drinking any water from a system that serves Millsboro and part of Dagsboro. Some of the 3,000 residents affected by the pollution episode relied on bottled water or supplies from emergency tanker trucks for weeks, with service restored only after the installation of a chemical filtration system.

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"The levels are significant at the property," Stiller-Banning said. "Our goal is to try to figure out how to clean it up and to remove any potential continuation" of the well contamination. She added that a cleanup could cost "several million" dollars, with the bill ultimately going to those responsible.