UPDATE: POLICE will investigate if vandals used keys sold on the black market for as little as $45 to take a train for a joy ride.

Crooks busted their way into the Hurstbridge depot, on Melbourne’s outskirts, at 1.50am this morning and then broke into a train despite security staff manning the site.

But the ride was short lived after automatic security equipment which derails rogue trains was activated after it trudged 80m.

The train then crashed into carriages, fencing and security boxes, with damage is estimated at $3 million.

media_camera The derailed train. Picture: Nicole Garmston

media_camera The damaged train. Picture: Nicole Garmston

The serious security breach has forced Metro to heighten all security at depots and the company is doing an audit of all depot and train keys.

Police have obtained CCTV of the brazen break in and spent the day probing the incident and interviewing witnesses, including cleaners and the security team who watched the incident unfold.

Metro chief executive Andrew Lezala said trains needed a combination of keys to start.

He suspected the ones used were stolen or lost.

“I suspect, somehow, they gained access to a key,” Mr Lezala said.

“Presumably they accessed that through the black market.”

media_camera Metro and police at the scene in Hurstbridge. Picture: Nicole Garmston

The Herald Sun found Metro keys, phones and uniforms for sale on social media and action sites on the internet.

Buses will continue to replace trains from Hurstbridge to Diamond Creek tomorrow, while all other services will run normally from Diamond Creek to the city.

Metro is in discussion with Public Transport Victoria to start using smart keys, enabling them to be cancelled if lost or stolen.

Rail, Tram and Bus Union secretary Luba Grigorovitch accused Metro of not taking their security seriously because it only hired 15 people in the network surveillance security team to patrol the entire network.

“This is not just about protecting trains from damage but also making sure that staff such as drivers are not exposed to the very real danger of being assaulted if they come across vandals when accessing trains parked at rail sidings,” she said.

“The network surveillance team needs to be expanded to a minimum of at least 50 staff and Metro must stop its practice of outsourcing security to private firms who lack any network operational knowledge as a matter of urgency.”

But Metro disputes the union figure and says it has 55 security staff patrolling the network at all times.

aleks.devic@news.com.au