(CNN) -- Thieves have forced the closure of Paris' Louvre museum. But an art heist was not the reason.
Instead, the closure came after staff walked off the job on Wednesday in protest against the increasing number of pickpockets operating in the museum.
According to a report in The Guardian, the pickpockets work in organized gangs and are targeting both tourists and museum staff with "increasingly violent tactics," including spitting and kicking.
Despite increased co-operation with the police and temporary bans on offenders, pickpocketing remains a growing problem for the museum, staff said.
The Louvre's press department was unavailable for comment early Thursday but a representative of the museum said the Louvre was "open as normal, until 5.30 p.m."
When pressed about yesterday's events, the representative declined to comment further and ended the call.
The Louvre also closed in 2009 and 2001 as a result of staff protests about industrial disputes and working hours.
The protest will be a pressing challenge for new director Jean-Luc Martinez as he takes up the post this coming Monday, taking over from Henri Loyrette.
The museum, home to famous works from masters such as Leonardo da Vinci, is the most visited museum in the world with around 10 million visitors last year.
Visitors should be mindful of their belongings when at the Louvre; Mona Lisa's eyes may not be the only things following you around the room.
The Louvre is open every day (except Tuesday) from 9 a.m. to 6 p.m. Night opening until 9:45 p.m. on Wednesdays and Fridays.
Musée du Louvre, 75058 Paris - France. www.louvre.fr