Hundreds of police officers, soldiers and emergency workers took part in a security exercise in the southern French city of Nimes on Thursday to test safety procedures at stadiums before the country hosts Euro 2016 this summer.
Around 1,200 police cadets and 700 emergency responders, partly in protective suits, were involved as extras in the exercise, which took place on the grounds of a police academy in Nimes.
The exercise simulated what would happen if a suicide bomber detonated himself in a stadium's fanzone and thereby release a chemical substance into the crowd.
"Not because there is a real risk of such an attack, but because we have to prepare ourselves out of caution for all hypothetical scenarios," Interior Minister Bernard Cazeneuve said.
"The exercise enacts [an explosion] in the fanzone of Marseille," said operation leader Jean-Cyrille Reymond.
Six European Championship matches, including a semi-final, are scheduled to take place in the Mediterranean metropolis' stadium, and as many as 80,000 spectators can also monitor parts of the fanzone.
"No sporting event in France has ever been so heavily secured," Sports Minister Patrick Kanner said.
The test-run was aimed at coordinating an inter-agency response among security forces in the case of a terrorist attack or similar crisis, with Kanner saying everything would be done to prevent a scenario like the one in the exercise from taking place.
Speaking earlier this week, Cazeneuve said that some 75 exercises are planned across France this year. More than 50 would take place before the start of Euro 2016, which is expected to draw a million foreign visitors to 51 games in 10 venues from June 10-July 10.
France has been in a state of emergency since 130 people were killed in a series of terrorists attacks in Paris on November 13, 2015. Euro 2016 planners said they have increased the security budget for the tournament by 15 per cent since then.