The father, daughter and a colleague of the father were taken into custody in Lyon on Monday, four days after they reported being the victims of a heist resembling the plot of a Hollywood movie.
The 22-year-old daughter told police she was kidnapped from her apartment in the southeastern French city of Lyon by two men posing as plumbers.
She said the men bundled her into a car, tied her up and forced her to telephone her father who works for SOS Surveillance, a Swiss company that transports cash in armoured vans, to demand a ransom.
French police last week estimated the loot at 20-30 million Swiss francs (17-26 million euros, $21-32 million).
Also Read
The daughter was found unharmed at around 10:00 pm on a road outside Lyon and appeared "very shocked" by her ordeal, police said at the time.
Investigators now appear to suspect it was an inside job.
Swiss authorities had appealed for witnesses to come forward over the robbery and said they were looking for three men with accented French, "maybe from the south of France or North Africa".
Disclaimer: No Business Standard Journalist was involved in creation of this content