A 22-year-old woman has died after the car in which she was a passenger rolled on Naughtons Gap Road between Casino and Bentley early this morning.
Three other occupants have been taken to hospital following the single-vehicle accident, which occurred at about 1.30am.
Police say the car hit a rail bridge, causing it to roll.
The 19-year-old male driver of the car was taken to Lismore Base Hospital for mandatory alcohol and blood testing and is assisting police with their inquiries.
Naughtons Gap Road was due to reopen to traffic at 8am.
ABC radio was this morning reporting delays on the Pacific Highway at Yelgun, near the rest stop, slowing traffic in both directions.
Byrill Ck crash
In yet another accident, two cars collided on Kyogle Road at around 3am.
No-one was killed but three people were taken to Tweed Hospital in serious but stable conditions.