A 19-year-old driver from Kalkara was critically injured when his Toyota crashed into a wall just outside the entrance of the Regional Road tunnel which takes south-bound traffic this morning.
The man was assisted by a medical team on site and taken to hospital.
An inquiry is under way.
The road was closed for the morning, creating traffic congestion.
The accident was the second of its sort within a few hours, with a young man having been injured when his car crashed into a wall at Hal Farrug during the night.