The revelations hit the press on Monday, with the publication of the testimony by Libération newspaper, but sources later told the Reuters news agency that an investigation into Octris's methods had been launched in December.
The investigation is based on the account of a man given the cover name of "Stéphane V" by the police, who claims to have also worked for the US's Drug Enforcement Agency and has now talked to Libération.
He claims to have occupied a villa near Marbella in southern Spain in March and April 2012 on behalf of Thierry.
Men presented to him as French police officers unloaded 19 tonnes of cannabis from Morocco on the beach there and then took it by car to France, he says.
The drugs were supposedly brought in as bait to catch traffickers but only some were intercepted and impounded, according to his account.
Top drug trafficker was informer
The rest went to Sofiane H, a convicted drug dealer who was an informer for Thierry, Libération suggests.
The operation allowed Thierry to present some major drug hauls to the press, often accompanied by ministers, but also eliminated Sofiane H's competitors and allowed him to flood the market.
Sofiane H was arrested and charged in April, following the seizure in October last year 7.1 tonnes of cannabis hidden in three vans near his luxurious apartment in Paris.
Thierry's partner, Anne Claire V, defended Sofiane H in a case in 2011 that led to his condemnation to 13 years in prison and his subsequent release after serving only three.
Former Lyon police chief charged
In a similar case former Lyon police chief Michel Neyret has been charged with corruption and drug trafficking after being accused of becoming too close to his gangland contacts.