Home-made explosives like those used previously by Islamic extremists were found on September 6 in an apartment outside Paris that French officials said might have been used as a lab for possible attacks.
Officials said they found triacetone triperoxide, better known as TATP, in the Villejuif apartment, as well as gas canisters and electric wiring, leading to the arrest of two suspects.
TATP has been used by the Islamic State extremist group, which has staged or inspired several attacks in France in recent years.
A tip from a repairman who was working in the building and noticed suspicious products led police to the apartment, Interior Minister Gerard Collomb said.
Police found substances that "may be used to make explosives" in the unit, Collomb said, praising the "civic reflex" of the worker.
A bomb-disposal operation was carried out in the apartment, police said.
Based on reporting by AFP and Reuters