Police have discovered the car of a Victorian woman missing for a week, but there's still no sign of the 22-year-old.

Sarah Cafferkey was last seen by her family at her Bacchus Marsh home on Friday 9 November.

She went out with friends that night and hasn't been seen since.

Police made a breakthrough in the search for Sarah last night when they discovered her abandoned silver 2001 Astra sedan in Owen Street, Maribyrnong.

This afternoon, police were door knocking the area where the car was found for more clues.

Worried friends and family say her disappearance is out of character.

They have flooded social media with appeals for information on Sarah's whereabouts.

The Facebook page 'Help!! Have you seen Sarah Cafferkey??' has attracted more than 2500 fans and dozens of posts, but, so far, no information as to where she is.

Police say Sarah's phone hasn't been used and her bank accounts are still being checked.

Sarah suffers from a rare form of asthma and her mother, Noelle Dixon, fears she may be unwell.

She told News Ltd yesterday: "It's called acute bronchial spasms.

"If she doesn't have her puffer and she doesn't get an ambulance to her she could die within half an hour."

Missing Sarah Cafferkey's car. Photo: Facebook

Ms Dixon said she had searched the local area and keeps an anxious vigil by her phone waiting for her daughter's call.

Sarah is Caucasian with a fair complexion, 168cm tall, thin build, black shoulder length straight hair with green eyes.

Anyone with information is urged to call 000 immediately.

Missing: Sarah Cafferkey