A $A1 million reward is being offered for information about a Melbourne teenager who vanished on her way to school in 2011.
Siriyakorn "Bung" Siriboon, 13, left her home in Boronia on 2 June, 2011, but never arrived at school.
A man was twice arrested last year - in August and then in October - and questioned over the disappearance, but both times was released without charge.
The girl's family and police on Tuesday announced a $A1 million reward for information leading to the arrest and conviction of those responsible for her disappearance.
Detective Inspector John Potter said officers were still missing the crucial piece of information that would give an answer about what happened to Bung, and he hoped the reward would encourage someone to come forward.
Wearing a blue and white school uniform and carrying a backpack, Bung left her home on Elsie Street at about 8.30am on June 2, 2011.
AAP reports she was seen by a neighbour a short time later on Elsie Street, walking towards Albert Avenue, but never arrived at school.