A seven-year-old boy and his elder sister have been killed during a fireworks display to mark France's national day in the western town of Cholet, reports the BBC.
"A rocket exploded in the middle of people," said Mayor Gilles Bourdouleix.
He described how the victims were with other family members 50m (160ft) from where the fireworks were being let off.
The explosion sent spectators fleeing in panic and left areas of grass in flames.
The boy was killed instantly and his 24-year-old sister died later of a heart attack, according to French reports. Seven others were hurt. Their parents suffered from shock, while a man described as close to the sister sustained serious burns.
Local prosecutors have opened an investigation for manslaughter.
Cholet was holding its first Bastille Day fireworks display for three years because of the Covid pandemic.