A teenage girl is dead and a young man has been arrested after a van they were travelling in crashed while being chased by police north-west of Melbourne.

The allegedly stolen Hiace van crashed into a stationary VicRoads truck near Ballan, spraying debris for hundreds of metres, about 2.30pm on Tuesday.

Police had been pursuing the van near the Ballan-Daylesford Road on the Western Highway for about four minutes when the crash occurred.

The girl died at the scene, while a male teen believed to be the driver of the stolen vehicle fled, triggering a manhunt in nearby bushland.