Protesting prison guards have clashed with police outside the sprawling Fleury-Merogis Prison in Paris on monday.
Things came to a head after a few hundred guards blocked the entrance and set tyres on fire to call attention to concerns about security and overcrowding.
Police tried to find a way to remove protestors from the blockade but faced resistance. As a result police fired tear gas to disperse the crowd.
The prison which is used for housing violent criminals and far right extremists is working at a 190 percent capacity.