Authorities were racing Monday to reassure the public about security at key cultural sites — and find the jewels stolen from the museum before they can be broken up and melted down.

The crew of chainsaw-wielding thieves who brazenly robbed The Louvre of priceless jewels in the highest-profile museum theft in living memory may have been hired by a collector, officials said. Paris Prosecutor Laure Beccuau said authorities are investigating whether the heist was commissioned by a collector.

It was on March 18, 1990, in Boston, when two thieves disguised as police officers stole a Rembrandt and a Vermeer valued at more than $500 million.

Never say never. The Mona Lisa (1503), undoubtedly the main attraction at the Louvre, was stolen in 1911 and recovered two years later. The thief, Vincenzo Peruggia, was an Italian handyman working at the Louvre and was caught trying to sell it.