In what could be the first major break in the investigation of the $102 million jewel heist at the Louvre Museum, police have found traces of DNA on items the thieves left behind in their hasty getaway,

The only camera monitoring the exterior wall of the Louvre where they broke in was pointing away from the first-floor balcony that led to Gallery of Apollo housing the jewels, she said. "We failed these jewels," she said, adding that no-one was protected from "brutal criminals - not even the Louvre".

Laurence des Cars, the Louvre's president and director, is set to testify about the heist before the French Senate's Culture, Education and Sport Committee on Oct. 22.

Thieves used a stolen truck-mounted moving lift to scale the Louvre and steal royal jewels worth over $100 million in a lightning-fast Paris heist.

Questions abound about how four thieves were able to make off with priceless, Napoleonic-era jewels — in broad daylight

The Louvre reopened earlier in the day to long lines beneath its landmark Paris glass pyramid for the first time since one of the highest-profile museum thefts of the century stunned the world with its audacity and scale.

About 100 investigators are now involved in the police hunt for the gems and heist suspects​, said prosecutor Laure Beccuau, whose office is leading the investigation.

Three masked thieves carried out the robbery in the Apollon Gallery on the museum's second floor, which overlooks the River Seine and is currently under construction.