The Serious Fraud Office has closed its investigation into Hawkins Construction without laying any charges.
Last August SFO investigators executed search warrants on two Hawkins premises and the $419 million upgrade of an electricity substation in Hobson Street, Auckland, that the company is project managing.
"Following a thorough evaluation where investigators considered thousands of documents, conducted interviews and obtained expert industry advice, the Office has concluded that there are no grounds to commence a criminal prosecution," SFO acting chief executive Simon McArley said today.
"While the manner in which the parties conducted their business appears to us to be unusual, we have evidence from industry experts that it is entirely possible that those involved honestly believed the conduct was legitimate.
"In light of that it cannot be concluded that the criminal threshold has been reached."
He added that the investigation had provided the SFO with a deep insight into the contracting and sub-contracting nuances of the construction industry.
While "a genuine concern was raised in good faith but not found to be substantiated" in the Hawkins case, Mr McArley did not believe that this would be the last time the SFO would look into industry contracts.
Hawkins Construction is one of New Zealand's largest construction companies.