The prosecutor’s statement didn’t say what role, exactly, the man is thought to have played in the daylight heist, carried out with angle grinders, a freight lift and subterfuge, with robbers dressed as workers in bright vests.

The robbery is believed to have been the work of a four-person team — with two people breaking into the museum’s Apollo Gallery where the jewels were displayed and then being whisked away on motorbikes by two associates who waited outside.

The haul hasn’t been recovered. 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 robbery has focused attention on security at the Louvre, the world’s most-visited museum.

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 that the two who broke into the ornate Apollo Gallery used grinders to cut into jewelry display cases.

The emerald-set imperial crown of Napoleon III’s wife, Empress Eugénie, containing more than 1,300 diamonds, was later found outside the museum.