A motorist was killed Wednesday night after he sideswiped another car in the southbound lanes of the Seaford-Oyster Bay Expressway, went off the road and hit a tree, police said.

The 23-year-old man, whose identity was not released, was pronounced dead at the scene, near Exit 5, at Route 107 in North Massapequa, Nassau County police said.

The accident occurred at 11:17 p.m., police said.

All southbound lanes were closed in the area from 11:28 p.m. Wednesday to 4:42 a.m. Thursday, according to the state Department of Transportation website.

His car, a 2001 Nissan Maxima, sideswiped a 2011 Nissan Altima that was driven by a woman, 24, whose identity was not released, police said. She was hospitalized for injuries that were not life-threatening, police said.

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At the scene, a crushed vehicle could be seen up against trees off the right-hand shoulder of the southbound lanes, just yards after Exit 5 ramp.

Officers placed evidence markers on the roadway, while others used flashlights to search the brush and trees.

With Ellen Yan