Police are investigating the circumstances surrounding a serious crash where four people were injured in a collision at Eungella just west of Murwillumbah this afternoon.

About 3:30pm a Toyota Corolla and a Holden Rodeo utility were travelling in opposite directions on Tyalgum Road, approximately 15km west of Murwillumbah, when they collided.

As a result of the crash the driver of the Toyota, a teenage male P2 driver, sustained serious head injuries and was taken to Tweed Heads Hospital in a serious condition.

The driver of the Holden, a man believed to be aged in his 40s, suffered minor injuries and was taken to Murwillumbah Hospital for mandatory blood and urine tests.

A 10-year-old girl who was a rear passenger in the utility suffered serious injuries and has been taken to the Gold Coast Hospital in a critical condition.

A woman, aged in her 20s, who was in the front passenger seat of the utility, was also taken to the Gold Coast Hospital in a serious condition.

Tyalgum Road has been closed while officers from the Ballina Crash Investigation Unit and specialist forensic officers conduct examinations of the scene.

Motorists travelling between Tyalgum and Murwillumbah are urged to avoid the area or use diversions through Chillingham and Crystal Creek.

Anyone who witnessed the collision and who has not yet spoken to police is urged to contact Tweed Heads Police via Crime Stoppers on 1800 333 000.