State police are still investigating a three-car accident on Interstate 287 North early Saturday morning that sent one person to Robert Wood Johnson University Hospital with a serious injury.

According to police, the accident occurred at mile marker 12.6 in Bridgewater at 4:38 a.m., and involved a tractor trailer and two other vehicles.

Police are still investigating the cause of the accident, and said there was only the one injury reported.

The right two lanes were shut down until about 9 a.m. while the investigation continued, but traffic was moving because not many vehicles were on the road at the time, according to police.

Police said the New Jersey Department of Transportation assisted with traffic.

Additional information about the cause of the accident was not immediately available.