The escape by helicopter of three inmates from a Quebec City detention centre in June was the product of a system-wide lack of preparation that could have been avoided, a government inquiry has found.

A summary of the administrative inquiry’s report was released Tuesday by Quebec Public Security Minister Lise Thériault.

Thériault told reporters that the whole report could not be made public because of court proceedings against the escaped prisoners and concerns that doing so would compromise correctional system security.

The summary of findings says the June 7 escape by the trio from Orsainville Detention Centre was predictable and should have been expected.

In 2003, Quebec's correctional services had produced an analysis of measures needed to prevent escapes by helicopter.

A previous escape by helicopter from a detention centre in St-Jérôme in March 2013 also meant Quebec's correctional system should have been better equipped and prepared to deal with a similar situation, the report said.

However, the report found that correctional officials underestimated the likelihood of a repeated attempt to escape by helicopter.

A government administrative inquiry into the St-Jérôme escape in 2013 took 15 months to report on the incident. Its recommendations only came out in July — a month after the Orsainville escape.

"If its recommendations had been made available earlier, their application throughout the correctional system would have made the escape on June 7, 2014, more difficult," concludes the summary of the latest inquiry's findings.

Officials with the Ministry of Public Security also underestimated the need for steel netting used at other detention centres in Canada and internationally to deter attempted escapes by helicopter.

Finally, the report found that Quebec's correctional services provided imprecise and incorrect information to cabinet about the June 7 escape.

Thériault was the focus of Opposition criticism for her handling of the situation in the days immediately following the escape.

Two helicopter escapes in two years

Yves Denis, 35, Denis Lefebvre, 53, and 49-year-old Serge Pomerleau were on trial on charges of drug trafficking at the time of their escape from Orsainvile Detention Centre. They were also facing murder charges.

The helicopter was able to land in a yard within the institution’s walls, where it met the men and flew them away.

The trio were recaptured on June 22 after police tracked them down to a condominium in Montreal’s Old Port district.

In the 2013 escape in St-Jérôme, two inmates climbed a rope into a helicopter hovering above the jail in a brazen daytime getaway.

Police located both men about 50 kilometres north of the jail later that same day.

After the Orsainville escape in June, three facilities — St-Jérôme, Rivière des Prairies and Orsainville — had air exclusion zones mandated.