Lille prosecutor Frederic Fevre said about 100 investigators were involved in the hunt for Redoine Faid, known for brazen attacks on cash-in-transit vehicles, after he blasted his way out of a jail in the northern town of Sequedin on Saturday.
Faid, a 40-year-old who risked a heavy new sentence over the 2010 death of a policewoman, used explosives to blast through five prison doors and took hostage four prison guards, who were later released.
Investigators were Sunday trying to determine how Faid had managed to obtain explosives inside the prison and whether he had any accomplices.
"A thorough investigation has begun. Obviously he had one or more accomplices. The investigators will now determine how he was able to obtain explosives and a weapon," Fevre told AFP.
French officials have warned that Faid is considered armed and "especially dangerous".
France has issued a Europe-wide arrest warrant and called in Interpol for help, amid fears he may have already fled across the border into Belgium.
Police have said the breakout was planned with meticulous precision and authorities have insisted there was no fault on the part of prison workers.
A getaway car used in the escape was found burnt in Lille, where Faid is believed to have switched to a second vehicle. Of the four hostages he escaped with, one was released just outside the prison, another a few hundred metres away and the last two along the highway.
Faid is known for co-authoring two books after a decade in prison for robbery, about his delinquent youth and rise as a criminal in Paris's impoverished suburbs.
He said his life of crime was inspired by American films such as "Scarface" and "Heat" -- where Robert De Niro's armoured car heist has been cited as the model for real life attacks in South Africa, Colombia and other countries.
"Movies for me were like a user's guide for armed robbery," he told the LCI news channel when his autobiography was released in 2010.
After his first robbery, Faid, of Algerian extraction, fled to Israel where he wore the Jewish skullcap and picked up Hebrew to blend in.
Despite vowing he had turned his back on crime, Faid was in 2010 suspected of being the mastermind of an armed robbery in which a young policewoman was killed in a shootout.
Faid, nicknamed "The Writer", landed back in prison in 2011 for failing to comply with his parole conditions and was due to serve the remaining eight years of his original sentence.
He potentially faced 30 more years over the policewoman's death.