Delabroye, the prison union rep, said the yard where the helicopter landed is the only area not equipped with anti-aircraft netting because inmates never use it - "except to leave the prison".
This picture taken on July 1, 2018 in Aulnay-sous-Bois, north of Paris shows a auto abandoned by French armed robber Redoine Faid at parking in a O'Parinor shopping mall after his escape onboard a helicopter from a prison in Reau. Faid serving 25 years for murder made an audacious escape from prison Sunday after a helicopter carrying several heavily armed commandos landed in a courtyard, freed him from a visiting room and carried him away.
Le Monde newspaper reported the operation only took a few minutes.
According to the Associated Press, Redoine Faid, who is serving 25 years for failed robbery and murder of a police officer, previously escaped another prison in 2013 using explosives hidden in packs of tissues before being rearrested a month later.
He was caught and placed back in jail by the French authorities within six weeks.
That same year, he wrote a book about growing up in Paris' suburbs and leading a life of crime, which he claimed at the time to have put behind him. French outlet BFMTV reports that the men, hooded and dressed in black, burst into the room at around 11:20 local time (09:20 GMT) on Sunday, demanding Faid's release. Faid's brother has been taken into custody for questioning. A police search is under way across the whole Paris region.
A huge police team have been dispatched to track down and recapture the fugitive, says France's Ministry of the Interior, who described Faid as "dangerous". He is said to be devoted to Robert De Niro movies and the stylised crime thrillers of USA director Michael Mann.
In 2001, three armed robbers fled a prison in Draguignan, southern France, after an accomplice hijacked a helicopter from an airfield in nearby St Tropez.
The 2010 robbery that he was imprisoned for involved the shooting of a female police officer.
But he was suspected of masterminding an attempted armed robbery in 2010 that led to a high-speed chase and a shootout with police in which 26-year-old policewoman Aurelie Fouquet was killed.
This wasn't the first attempt of the 46-year-old to break out of prison. One of Faid's most recent prison supervisors said he was never in conflict with guards, but that "we must always be wary".