A coach bus flipped over into oncoming traffic on the Long Island Expressway shortly before midnight Monday, killing two people and injuring 10 others, according to New York City authorities.

The bus was traveling west when it collided with a vehicle near Exit 16 onto Greenpoint Avenue, setting off a collision with four other vehicles, according to a Police Department spokeswoman.

The bus then flipped over the median into incoming eastbound traffic, the spokeswoman said, adding that the information was preliminary.

The driver of the bus and one passenger were pronounced dead at the scene, the police said.

Twenty people were taken to local hospitals for injuries, including three with critical injuries, the Fire Department said in an email.

The two victims were not identified. It was also unclear what had caused the crash.

The authorities said that they were still investigating, and that they had blocked all lanes eastbound and westbound on the Long Island Expressway at 50th Street.

About 79 fire and emergency services personnel responded, and operations were ongoing, the Fire Department said.

As of 5 a.m. on Tuesday, the westbound Long Island Expressway remained closed at 50th Street and Queens-bound traffic was being diverted, according to the authorities, who said there were major delays and urged travelers to use alternate routes.