The CFMEU has rejected a claim of sabotage over a deliberately lit fire at a Grocon building site in Melbourne, saying it is a matter for police.
Grocon is claiming the fire at its Collins Street office block development on Friday is part of a string of sabotage incidents and it will refer it to police.
"This is yet another criminal act of sabotage carried out by people with no respect for the law, workplace safety or human life," Grocon spokesman Dan Blyde told News Ltd.
The CFMEU released a statement on Saturday, saying any suspicious circumstances surrounding the blaze should be handled by authorities.
"The implication made by Grocon, as reported in the Herald Sun that this fire has been lit as some kind of industrial tool, is completely rejected by the CFMEU," union national construction secretary Dave Noonan said.
"It should be backed up by hard evidence or it should be withdrawn."
Mr Noonan says the union condemns arson because it endangers lives and anyone behind such acts shouldn't be working in the industry.
"While it is no secret that the union is critical of Grocon's safety record there would never be any circumstances under which the CFMEU would sanction arson or sabotage as an industrial weapon," he said.