Security officials said robbers bored through an underground wall into the Credit Lyonnais bank on Avenue de l'Opera, between the Louvre and the old Opera house in the heart of tourist Paris on Saturday.
The branch was closed for renovations, but a security guard who heard noises from the basement was confronted by three individuals, who overpowered him, lashed him to a chair and ordered him not to move.
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Meanwhile, the gang used drills to cut a hole in the thick wall of the vault just large enough for some of them to squeeze through and ransack the safety deposit boxes of 125 clients, LCL said.
The bank would not give a figure for the total number of boxes at the branch office.
Bank set on fire to cover gang's tracks
Just after 7am on Sunday, the guard, who could no longer hear drilling and could smell acrid smoke, raised the alarm.
The gang had abandoned their tools and set fire to the premises to disguise any clues to their identity.
Witnesses said they saw four or five men leaving the area in a van.
The bank said the guard was in good health but undergoing medical and psychological screening after his night-long ordeal.
Police said identifying and putting a value on what was missing would be a long and difficult task, and that the gang appeared to have been equipped with sophisticated tools for what was otherwise a very traditional robbery.
The raid bore strong similarities to a strike in September against another bank undergoing building work, this time in Seine Saint-Denis in the northern Paris suburbs, in which 117 safe deposit boxes were emptied.
