Thirty-one people were killed in an explosion at the AZF fertiliser factory in Toulouse in 2001.
France has held a memorial to mark the 20th anniversary of a deadly factory explosion in Toulouse.
Thirty-one people were killed and thousands injured in the blast at a fertiliser factory near the city on September 21, 2001.
The explosion completely destroyed the chemical plant in France's biggest industrial disaster since the Second World War.
On Tuesday, local officials, firefighters, and members of the victim's association commemorated the disaster with a minute's silence.
The names of the 31 victims were read out before wreaths of flowers were then laid at the foot of the memorial.
"Our thoughts are with the victims and their families. France remembers," tweeted French President Emmanuel Macron, who was not in attendance.
Prime Minister Jean Castex added that the explosion had left France in a state of "shock and awe".
"The nation respectfully bows its head in memory of the victims," he added on Twitter. "My thoughts are with the people of Toulouse, whose emotions are still alive and whose memories are still intact."
The deadly blast in 2001 was caused by more than 300 tonnes of ammonium nitrate stored in a hangar at the AZF chemical complex.
The explosion, five kilometres from the centre of Toulouse, measured 3.4 on the Richter scale.
After a legal battle lasting 18 years, a French court in 2017 found the former director of the factory site guilty of "gross negligence".
Serge Biechlin was sentenced to 15 months in prison and fined €45,000. Meanwhile, the company that owned the plant -- Grande Paroisse -- was ordered to pay a fine of €225,000.
Both have rejected allegations that they failed to comply with safety obligations and denied the charges.
Relatives of the victims have long accused the company, a subsidiary of Total, of failing to acknowledge responsibility for the explosion.