Victoria Police have launched an internal investigation after two teenage boys were repeatedly sprayed with capsicum foam – because one did not have a valid railway ticket.

Disturbing CCTV footage was aired on the ABC's 7.30 program on Thursday evening, after the Children's Court made the unusual decision to allow reporting on the incident.

PSOs drag 'Stephen' from a train at Springvale station last year. Credit:7:30

One of the teenagers had been charged with assaulting Protective Services Officers Michael Rice and Matthew Sargent. But Magistrate Gregory Connellan acquitted the young man last month after finding there was no evidence he intended to assault or hinder the officers.

Instead the magistrate found there was nothing in the teenager's behaviour or body language to justify being sprayed, while some allegations and evidence made by Officer Sargent were found to be false.