A driver has been arrested after a man was killed in a crash between a car and a van.
It happened near junction 25a westbound on the M4 at Newport at about 03:30 BST.
Gwent Police said the driver of the car, a 45-year-old from the Ebbw Vale area, died.
A 23-year-old man, from the Cwmbran area, has been arrested on suspicion of death by dangerous driving and failing to stop. He remains in custody.
The Brynglas Tunnel was closed westbound between junction 25a and junction 26 while investigation work took place but has since reopened.