A man is in custody over a fatal hit-run in Melbourne’s west that’s left a young woman dead and a major road closed.

Her body was found on Ballarat Road at Ardeer, shortly after 7.30pm on Monday night.

She’s believed to be aged in her 20s or 30s.

The 31-year-old Cairnlea man came forward to police early on Tuesday morning and is currently in custody assisting police.

The westbound lane of Ballarat Road is currently closed between the Western Ring Road and Hulett Street and police are asking motorists to avoid the area.

Anyone who witnessed the crash or with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report at www.crimestoppersvic.com.au