Emergency workers performed CPR on a man pulled out of the water in serious condition as Suffolk detectives were investigating a report that a motorist had driven off the Port Jefferson boat launch Thursday afternoon, witnesses and authorities said.

Several police and firefighters worked to pull a submerged vehicle from the water and Suffolk County police Marine Bureau divers examined the wreckage, including using a thermal imaging camera to determine whether anyone was still trapped inside.

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But it was unclear exactly what had happened or if anyone else was hurt in the 5:30 p.m. incident at the dock at West Broadway and Barnum Avenue.

Sixth Squad detectives said the man who was pulled from the water had serious injuries.