UPDATE: 2.15pm

A spokesman for the Welsh Ambulance Service said all four were taken to hospital, three of them to Nevill Hall Hospital and one to Prince Charles Hospital all with serious injuries.

UPDATE: 1.42pm

All four of the 17-year-olds remain in hospital, with two having what polie say are "life-changing injuries".

They are all from Abergavenny.

UPDATE: 8.47am

Fire crews had to cut the roof off to move the two passengers out of the back of the car for medical reasons.

A spokeswoman for the South Wales Fire and Rescue Service said the driver and front seat passenger were able to free themselves from the car.

UPDATE: 6.35am

FOUR teenager boys were injured in a crash near Abergavenny last night.

Gwent Police, the South Wales Fire and Rescue and Ambulance Services were called to the B4269, known locally as Gypsy Lane, between Llanellen and Llanfoist at 10.48pm.

Three fire engines and a rescue tender were sent to the scene.

The 17 year-olds were treated for their injuries which are still being assessed.

The road was closed for several hours and re-opened at around 5am this morning.

Gwent Police is appealing for anyone who may have witnessed the collision to call 101 quoting log number 502.