According to a report in the Newark Star-Ledger, state police spokesman Sgt. Stephen Jones said Smith and Andre Bell were ejected from Smith's SUV in the crash.
The crash occurred around 5:30 p.m. on Stagecoach Road in Millstone Township.
ESPN.com's Andy Katz spoke with Nuggets front office executive Bret Bearup, who told Katz that the Nuggets have spoken to Smith. Bearup said that while Smith sustained bumps and bruises in the accident, his injuries are not life-threatening.
The Star-Ledger reports that Bell suffered serious head wounds and was airlifted to Jersey Shore University Hospital in Neptune, where he was listed in extremely serious condition Saturday night. Smith was also taken there via ambulance.
The driver of the second vehicle, as well as Carl Marshall, the second passenger in Smith's SUV, also were injured. They were taken to CentraState Medical Center in Freehold, but neither had serious injuries.
Marshall, a basketball player at Seton Hall, had just completed his senior season.
Smith's father, Earl, told the Star-Ledger that J.R. was "fine -- he was thrown from the vehicle, but there's no injuries. He was with two friends, coming home from a barber shop."
According to the police report, the accident happened after Smith's vehicle went around a vehicle stopped at a stop sign on Stillhouse Road where it intersects with Stagecoach Road in Millstone Township.
The police report said that after Smith continued into the intersection, his car was hit by another car, which had the right of way. The impact overturned Smith's SUV, tossing out Smith and Bell in the process.
Smith and Bell, according to the report, were not wearing seatbelts while the driver of the other car and Marshall were wearing seatbelts. The airbags in the other vehicle deployed.
The 21-year-old Smith was a star player at Lakewood High School
and St. Benedict's Prep in New Jersey. He averaged 13.0 points in 63 games this season.
Information from The Associated Press was used in this report.