Police reinforcements were detailed to the RER suburban train network on Tuesday afternoon, two and a half days after the crime took place, until further notice.
The move followed headlines reporting a “savage attack” in the media Tuesday morning.
The incident in question took place at 10pm on Saturday when a group of youths, about 20 according to witnesses, jumped on a train in the town of Grigny and sounded the alarm to stop it.
The youths, who had their faces covered and were armed with teargas, then worked their way down the carriages, robbing wallets, handbags and mobile phones.
There were eight or nine victims, six of whom have reported being attacked, according to police.
“I was hit and had teargas sprayed in my eyes,” one victim told the press. “They grabbed my girlfriend’s handbag and took my money. It was fast, violent and seemed to be very well organised.”
“It’s like a modern-day stagecoach robbery,” an anonymous police officer commented.