STATEN ISLAND, N.Y. -- Three off-duty officers from the Linden Police Department were among the four passengers in the vehicle involved in a head-on collision with a tractor-trailer on the West Shore Expressway Friday morning, the chief of the department confirmed.

One of the off-duty cops was among the two fatalities in the accident, the chief said. WPIX 11 reported that the fourth passenger was a civilian employee at the department, but the chief could not confirm that.

The chief said he could not release the identities of the officers.

The tractor-trailer was driving southbound on the West Shore Expressway and the officers' vehicle was traveling the wrong way in the southbound lane before the two crashed just before 5 a.m., according to an NYPD spokesman.

The driver and front passenger in the vehicle were pronounced dead at the scene and the driver of the tractor-trailer was taken to Richmond University Medical Center, West Brighton, with minor injuries, the spokesman said.

The two backseat passengers in the vehicle suffered serious but non-life threatening injuries, police said. One was taken to Staten Island University Hospital, Ocean Breeze, and the other to Richmond University Medical Center, West Brighton.

There were six total patients, including one firefighter who suffered minor injuries, an FDNY spokesman said.

The cause of the accident is still under investigation.