A man was seriously injured Saturday afternoon when he jumped or fell out of his SUV while driving on the Long Island Expressway, Suffolk County police said.

Firefighters found Christopher Wilson, 40, of Huntington Station, lying in the left lane of the eastbound LIE near Exit 51 shortly after receiving a 911 call at 1:18 p.m.

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He was airlifted to Stony Brook University Hospital, where he was listed in serious condition last night, authorities said. "He had severe trauma all over his body," said Dix Hills Fire Chief Tom Magno. "His whole back was road-rashed."

Wilson's abandoned vehicle, a 1993 Chevrolet Blazer, continued on for another quarter-mile before striking a light post on the south side of the roadway and hitting some trees, police said.

Detectives are investigating whether Wilson fell out or jumped on purpose. No cars struck him. The LIE was closed eastbound for three hours because of the incident, according to the state Department of Transportation website.