A strong gas odor overcame a Bay Shore neighborhood just before sunrise Saturday, in the area of Lanier Lane and Cooper Lane between Union Boulevard and Montauk Highway, authorities said.
No homes were evacuated, Suffolk police said, but neighbors worried, especially in light of news of government testing of possibly toxic substances.
Tom Stringer of Lanier Lane in Bay Shore described the stench as hitting him "like a brick wall."
"When you smell something like that you are fearful that something catastrophic is going to happen," he said Saturday.
National Grid, the utilities company, is replacing gas lines in the area.
The county is joining in an effort to test groundwater wells near a toxic plume because elevated toxins have been found in water pumped from under a home in the area.
Previous tests of water in the area showed elevated levels of a possible carcinogen.