Homemade TATP explosives ready for use were found Wednesday in an unoccupied flat near Paris, judicial sources said.
Gas canisters and electric wiring were also found in the flat near Villejuif, south of the French capital, and two men were arrested, the sources said.
TATP is the explosive of choice of the Islamic State group (IS), which has repeatedly targeted France in recent years.
Police also found ingredients that can be used to produce TATP as well as papers written in Arabic.
Anti-terror prosecutors have opened an investigation, sources close to the probe said.
One of the two arrested men, aged 36 and 47, is the owner of the flat, they said.
Paris police said a man who works at the apartment block had alerted police to “suspect items” in the apartment.
France has been under a state of emergency since IS jihadists struck in Paris in November 2015, leaving 130 people dead.
Since that large-scale attack and last year’s Nice truck attack that killed 86, France has suffered a string of smaller assaults mainly targeting security forces.