The Garda Síochána Ombudsman Commission is investigating a two-car collision on the M8 motorway in north Co Cork, in which a teenage boy was killed and five other people injured.
Among those injured were four teenagers and a woman in her 30s.
The boy who died has been named as 16-year-old Johnny Foley from Spur Hill in Cork city.
The incident happened 2km outside Mitchelstown at around 1am.
The car in which the teenagers were travelling was going in the wrong direction on the northbound carriageway of the motorway.
The car had been reported stolen to gardaí earlier this week.
Forensic road crash investigators worked throughout the day to gather evidence.
The other four teenagers in the car, one of them a girl, were brought to Cork University Hospital (CUH) for treatment of injuries described as non-life threatening.
Johnny Foley was a passenger in the car.
A woman in her 30s from Cork was the driver and sole occupant of the second car. She was seriously injured and is also being treated at CUH.
The two cars collided head-on.
The crash is being investigated by gardaí in Mitchelstown. They have appealed for witnesses, particularly those with dashcam footage, to contact them.
The Garda Siochána Ombudsman Commission is conducting its own investigation into this incident, as gardaí say there was an interaction between them and the teenagers' car prior to the collision.
The referral to GSOC was made by a garda superintendent.
The M8 motorway has re-opened between junctions 12 and 13 near Mitchelstown in Co Cork, following this morning's fatal road crash.
This section of the motorway had been closed throughout the day, with motorists travelling in both directions diverted onto local roads.
Garda forensic road crash investigators have completed their examination of the scene.
