Police have arrested the 18-year-old driver of a ute that crashed south-west of Sydney on Tuesday night, killing five high school friends and leaving people in a small rural community grieving

Flowers are laid for the five teenage victims of a car crash at Buxton, south-west of Sydney, all students from Picton high school

Police said the man suffered non-life-threatening injuries and was treated by New South Wales ambulance paramedics before being taken to Liverpool hospital for mandatory testing.

Three girls, two aged 14 and one 15, and two boys, 15 and 16, died in the single-vehicle crash

The Picton high school teens were travelling in a Nissan ute being driven by an 18-year-old man when it left the road and hit a tree near the Wollondilly shire village of Buxton about 8pm

The impact tore the ute apart and all five passengers died at the scene

Acting Inspector Jason Hogan said the driver returned a negative breath test at the scene but was yet to be formally interviewed