A multicar accident shut down the entire eastbound Long Island Expressway just east of Exit 51, authorities said Thursday night.
Police said the dump truck fled.
At least two drivers were injured, including an 84-year-old man who was airlifted with chest trauma to Stony Brook University Hospital and a woman with minor injuries who was taken to Good Samaritan Hospital Medical Center in West Islip, said Robert Fling, first assistant chief with the Dix Hills Fire Department, which responded to the crash.
Police said the man's injuries were not life-threatening.
It appears the man's sedan had crashed into the center divider, bounced off and flipped over more than once, landing on its wheels in the HOV lane, Fling said.
It happened near Exit 51, which is Deer Park Road, he said.
"There was considerable damage all throughout the car," the Dix Hills chief said. "There was debris all over the place."
Police emergency services units had to cut the car roof off to free the injured man, Fling said.
Another man refused medical attention at the scene, but it was not clear how he was involved in the accident, the chief said.
Other details of the accident were not immediately available as officers investigated, police said.