The Ontario Provincial Police has “insufficient evidence” to lay charges in the ORNGE air ambulance scandal, following a six year investigative probe of kickbacks.

“The lack of accountability and transparency in the (ORNGE) business records, the variance in perspectives and the lack of cooperation of key persons involved collectively has prevented an evidence-based finding from being made,” the force says in a detailed investigative summary.

ORNGE is the province’s government-funded air ambulance system. A series of Star stories on financial and safety irregularities with the vital service led to a complete overhaul of the agency in 2012. Top bosses including Dr. Chris Mazza, the president, were shown the door and a new board of directors was brought in. The OPP began an investigation in February 2012 focusing on allegations that the Italian company that supplied $144 million in helicopters was overpaid by ORNGE, and $4.7 million was flowed back to a company controlled by Mazza.

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In a lengthy document the OPP released Thursday morning, huge portions dealing with what investigators turned up are blacked out. In some cases they refer to the cost increase from the original purchase price of the helicopters to a new, higher price.

Another section, described as “perspectives” and headlined “Dr. Chris Mazza” is completely blacked out. The perspectives of other top officials are also blacked out in the report.

The OPP sought information in the U.S. and also in Italy, but according to the report detectives were stymied. Details related to the paying of money back to a Mazza-controlled company under a “marketing services agreement” remain “unclear and unexplained.”

In conducting the probe, OPP detectives considered charges of fraud, breach of trust and misappropriation of funds, the OPP document states.

At the end of the day, after six years, police say “no investigative steps currently exist that will assist in or compel the gathering of independent and reliable evidence upon which to form reasonable grounds” that a criminal offence was committed.

“Pending the receipt of additional evidence in the form of business records, cooperation of witnesses, or other information, this investigation is concluded.”