Police have revealed they made an October arrest in relation to a fire which shut down Yallourn Power Station last year, an event investigators say was caused by sabotage.
While investigation manager Detective Sergeant Alan Rumble said the arrested man was brought in for questioning over the incident, in which a high voltage circuit was allegedly tampered with, he was later released without charge.
Seven months into the investigation, police have gone public with the allegation in hope of being contacted by someone with knowledge of the incident, as first reported in Monday's Express.
The fire, which occurred during a fierce industrial dispute between station owner EnergyAustralia and station employees, began only 30 minutes after worker representative unions were officially emailed notification of the company's intentions to lock out its 75-strong operator workforce.
Det Sgt Rumble said one or more people with "knowledge of plant processes and equipment" - who also possessed approved access to the circuit board area - were likely responsible for the incident.
The Construction, Forestry, Mining and Energy Union have since said in a statement it was "gravely concerned" by the sabotage reports.
"It has always been the understanding of the union that the fire was caused by an electrical fault (and) would expect if police have evidence of the sabotage they would act," the statement read.
Victorian mining and energy minister Nicholas Kotsiras said he was concerned by the allegation.
"No group or individual should be able to threaten the safety of workers and critical infrastructure which all Victorians rely on," Mr Kotsiras said.
"These matters are being investigated and, if found true, should be dealt with the full weight of the law."