DEVASTATED friends and family of five people killed in a horror smash near Lara on Saturday have maintained a vigil at a makeshift roadside shrine at the site of the tragedy.
Investigators are still trying to piece together how a speeding BMW came to be driving erratically on the wrong side of the Princes Highway before ploughing head-on into a Subaru WRX loaded with six young friends about 1am.
The crash instantly killed the driver of the BMW, Sarah Houlihan, and four of the six friends in the Subaru, leaving another man fighting for his life.
Among the dead were young mother Casey Valetic, 24, of Hoppers Crossing, her best friend, Melissa Parry, 23, Nathan Kerr, 23, and Brad Dickson, 23 - all from Werribee.
The driver of the Subaru remains in The Alfred hospital in a stable condition.
Mourners returned to the scene on Sunday bearing flowers and balloons to pay tribute to the dead.
Casey Valetic was remembered by one friend as an outgoing, strong-minded woman who wore her heart on her sleeve.
''She's left behind her daughter Annabel and that's a piece of her she's left for us to treasure.''
A spokesperson for the family of Ms Houlihan, 32, said she was loved and respected.
''The family wish to express their sadness at this indescribable time for all involved and ask that all involved are given the time they need to grieve.
''Sarah was a loving, fun, caring and happy person. She was a respected natural health practitioner and teacher in her field. She was a qualified naturopath, homoeopath and nutritionist.''
Online tributes for Ms Houlihan continued to flow on Facebook on Sunday.
Assistant Commissioner Jack Blayney said a number of witnesses have come forward to say they saw the Ms Houlihan's car travelling on the wrong side of the freeway.
''Obviously we're looking for anybody else that may have seen this vehicle at an earlier stage, particularly on the wrong side of the freeway, to come forward to police so that we can actually piece this story together to get some clarity around what's happened,'' he said.
''Clearly something has drastically gone wrong here.''
With KRISTIAN SILVA