A GANG of vandals broke into secure rail yards in Ballarat and painted three brand new train carriages destined for Melbourne's metropolitan network.
Rail manufacturer Alstom is producing the carriages along with the X'Trapolis trains for rail services operator Metro in a multi-million dollar boost for Ballarat.
But police as many as eight trespassers broke into the company's Creswick Road rail yards and covered the carriages in graffiti.
A police spokeswoman said the carriages had been painted "top to tail".
"It's about $50,000 worth of damage," she said.
"They were disturbed by security at about 6am this morning, but we believe they had been there for several hours before that."
Crime Scene Services officers, along with detectives from the Ballarat Criminal Investigation Unit, are now on scene.
No arrests have yet been made and no descriptions of the offenders have been released at this stage.
Anyone with information on the criminal damage can call Ballarat Criminal Investigation Unit on 5336 6080.