NOEL KING, HOST:

Good morning. I'm Noel King. Something is in the air in Delaware County, Pa. Residents there say a mysterious smell is back. One woman told Philly's local CBS station it was like sulfur. Another said she's afraid to smoke in case it's a gas leak. It comes and goes, and officials have looked for the source for months now. Agencies from three states have formed an odor investigation task force. So please, if you smell something, say something. Transcript provided by NPR, Copyright NPR.