The suspects are two men aged 38 and 39 and two women aged 31 and 40, a statement by Laure Beccuau said.
Her statement did not say what role they are suspected of having played in the October 19 theft.
Police can hold them for questioning for 96 hours.
French media reported that one of those arrested, a 39-year-old already known to police services, is believed to be the fourth member of the team thought to have carried out the daring daylight robbery and is from Aubervilliers, a suburb north of Paris other suspects have connections with.
Four other people were already arrested and placed under formal investigation on October 29 and November 1, the prosecutor said.
The daylight robbery, in which four thieves made off with jewels worth $US102 million ($A158 million), raised doubts over the credibility of the world's most-visited museum as a guardian for its myriad works.
The thieves took less than eight minutes to force their way into the museum and leave, using a freight lift to reach the building's window.
Footage from museum cameras showed two broke into the ornate Apollo Gallery, cutting into the jewellery display cases with disc cutters and making off with the trove, while two riders on scooters whisked them away.
So far, no trace has been found of the stolen jewels.
It includes a diamond-and-emerald necklace Napoleon gave to Empress Marie-Louise, jewels tied to 19th-century Queens Marie-Amélie and Hortense and Empress Eugénie's pearl-and-diamond tiara.
The emerald-set imperial crown of Napoleon III's wife Empress Eugénie, containing more than 1300 diamonds, was later found outside the museum.
with AP
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