French anti-terrorism forces have arrested four people, including a 16-year-old girl, and uncovered a makeshift laboratory with the explosive TATP, the Paris prosecutor's office said.
The arrests were made in the Montpellier area of southern France.
The prosecutor's office said around 70 grams of TATP were seized.
The explosive, which can be made from readily available ingredients, was used in the November 2015 attack in Paris and the March 2016 attack in Brussels.
One of the suspects was believed to be planning a suicide attack, a Paris police official said.
The TATP and other base ingredients for fabricating a bomb were seized in the home of a 20-year-old man in the Montpellier area.
Two other men were arrested, a 33-year-old and a 26-year-old, along with the 16-year-old girl, according to the prosecutor's office, which handles terrorism investigations in France.
The investigation has not yet uncovered a specific target, a police official said.