Workers install metal security bars over the window where thieves broke into the Louvre museum in October. Emma Da Silva / AP

A crane was stationed outside the Louvre Museum in Paris on Tuesday — but this time it wasn't being used by jewel thieves stealing some of the nation's historic treasures.

Instead, the machine was operated by maintenance workers in security helmets and high-visibility vests as a crew installed metal bars to the now-infamous second floor window.

A team of thieves posing as workers used a basket lift to break in through that window on Oct. 19. The robbers entered the museum's Apollo Gallery and smashed open display cases to steal nine pieces of jewelry. All four suspected thieves have been arrested and charged, but none of the jewels have been recovered except for a crown that was dropped as the group escaped.

The theft exposed security lapses at the world's most-visited museum. A recent security audit found that 35% of the rooms in the Denon Wing, where the stolen jewels were displayed, are not monitored by security cameras, according to Radio France. The gems were also not privately insured, in accordance with French law.

Other security upgrades are coming, the museum's director said in November. Installation of new anti-intrusion systems was set to begin by early December, while more than 100 new cameras are expected to be up and running by the end of 2026, CBS News previously reported.

The Louvre didn't publicly comment on Tuesday's security operation. Samuel Lasnel of maintenance lift company Grima-Nacelles said he and his crew arrived before dawn Tuesday to carry out the high-profile window-securing assignment.

"We have already worked at the Louvre — on the interior, on the exterior, inside and outside the pyramid — we've been here several times," he told The Associated Press. "The Louvre knows us well."

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