At about 4.00pm on Thursday afternoon about 30 prisoners took refuge in a wing of the
prison and destroyed light fittings, flooded a gangway, destryed surveillance cameras and blocked passages with furniture, a prison warden told LCI TV.
With a summer heatwave pushing temperatures well above 30°C, tempers ran short and anger erupted when authorities told turned down their request to wear shorts, an item of dress that is strictly forbidden by France's prison regulations.
Special units intervened to reestablish order at 7.00pm.
Bourg-en-Bresse is one of France's few jails that is not overpopulated.
Bulit in 2010, it has 700 places, if which 90 per cent are occupied.