More than 2,000 people from the French emergency services took part in a fake chemical attack designed to give them the best possible training should the tournament by targeted.
The activities undertaken were also in response to the terrorist attacks that took place in Paris on Friday, November 13 last year which left 130 dead and hundreds injured.
The Stade de France, which will host the final of Euro 2016 on Sunday, July 10, was a target of suicide bombers during the international friendly match between France and Germany but they were prevented from gaining entry into the stadium.
There are currently heightened security measures in place following the attacks in Belgium’s capital of Brussels last month left 32 people dead.
Extra security checks were put in placeat stadiums across Europe for the recent international break and it is expected that they will only become more stringent when the tournament gets underway on Friday, June 10.
More than 2.5 million fans are predicted to attend matches in ten host cities with a further seven million expected in fan zones during the competition.
Fan zone security is believed to be costing up to 17 million euros ($19m), with UEFA promising three million euros after the November’s attacks.
France will host Romania inside the Stade de France shortly after the opening ceremony and UEFA executive committee vice-president Giancarlo Abete has said that matches will not be played behind closed doors.
Saint-Etienne has been one of the host cities is be tested most recently and the Geoffroy Guichard Stadium was flooded by officials wearing chemical protective clothing.
The stadium will play host to four matches during the tournament. Portugal’s game with Iceland in Group F will be the first to play there on Tuesday, June 14.
Czech Republic against Croatia in Group D as well as Slovakia vs England in Group B will also be played out inside the 42,000 capacity ground.
The last match to be played there will be the round of 16 match between the runners-up of Group A and Group C on Saturday, June 25.
The mock attack tested the reactions of the authorities. Over a thousand police trainees dressed up as football fans and attempted to leave an isolated area following a ‘chemical explosion’.
The explosion sent a cloud of gas into the air and alerted the trainees that the training drill had started and that they were to act as if they were dealing with a real life event.
The pictures from the drills show medics treating people after the explosion and represent a realistic re-creation of a chemical-style terrorist attack.
Interior minister Bernard Cazeneuve said that training at Saint-Etienne, which will be replicated throughout France before the summer, was essential.