On the day of the heist, the robbers arrived at 09:30, just after the museum opened to visitors, Beccuau said at a press conference on Wednesday.
The suspects arrived with a stolen vehicle-mounted mechanical lift to gain access to the Gallery of Apollo via a balcony close to the River Seine. The men used a disc cutter to crack open display cases housing the jewellery.
Beccuau said the thieves were inside for four minutes and made their escape on two scooters waiting outside at 09:38, before switching to cars and heading east. Nobody had been threatened during the raid.
France’s justice minister said security protocols in the Louvre – one of the world’s most famous museums – “failed” in preventing the theft.
It was later revealed by the Louvre’s director that the only camera monitoring the Gallery of Apollo was pointing away from a balcony the thieves climbed over to break in.
Since the incident, security measures have been tightened around France’s cultural institutions.
The Louvre has transferred some of its most precious jewels to the Bank of France following the heist. They will now be stored in the Bank’s most secure vault, 26m (85ft) below the ground floor of its elegant headquarters in central Paris.