The hunt is on for four men over a string of failed attempts to entice children into vans, with schools issuing a "stranger danger" warning to parents.
In the past month, men in white vans have approached four students aged 10 to 15 years in Melbourne suburbs.
All the children escaped by running away or declining the offer and walking away before raising the alarm.
Schools have told parents to "reinforce the importance of having stranger danger conversations".
"The safety of all students is our top priority, and we are of course concerned by this recent spate of incidents," a Department of Education spokesperson said.
The most recent incident happened on Tuesday when a man in a white van approached a 10-year-old boy in Boronia in the city's east about 10.30am.
A day earlier at 9.40am, another man asked a 15-year-old girl walking along a Doncaster street to get in his van, but she was able to escape and sought help at a nearby shopping centre.
A similar approach was made to a 14-year-old girl in Tullamarine at 5.45pm on November 27.
The first incident that police are aware of happened on November 18, when a man told an 11-year-old boy in Blackburn that his mother had asked him to give the student a lift.
No suspects have been identified and investigators believe four different men were involved, Acting Superintendent Paul Cripps said.
"There are similarities - being a white van - but at this stage we haven't been able to establish any links between the offenders," he told reporters in Rowville on Thursday.
All of the incidents involved "malicious intent" but the children are doing well despite it being a scary experience for them and their parents.
The approaches were concentrated around schools, prompting police to step up patrols in affected areas.
The jump in reports of children being enticed into cars is one of the highest priority investigations for the force, Act Supt Cripps said.
All the men took a "friendly approach" when speaking with the children and used similar language, with slight variations in the descriptions of the vans involved.
"One thing we have to take into account, we are dealing with children so their descriptions aren't always as accurate," he said.
Parents are encouraged to "be alert but not alarmed" and have a discussion with their children about what to do if they are approached.
"Tell them what to do in these situations - not to get into vehicles, safety behaviour, speak to their parents, or teachers, report it immediately and let us know about it," he said.
