Two men have been arrested after police found components that can be used to make explosives in an apartment in a Paris suburb which media reports describe as a "bomb factory."
Security forces rushed to the scene after a plumber working in the building in the southern suburb of Villejuif saw what he thought resembled detonators and called the police.
The building was evacuated and work ordered to be stopped on a building site next to the apartment block while bomb disposal experts examined the material.
The flat was empty at the time of the discovery of the suspect devices and the two men were arrested in a car in the nearby suburb of Le Kremlin-Bicetre, media reports said.
One of them was reportedly the tenant of the apartment.
France Info radio said that the flat was like a "laboratory" and contained sulphuric acid, acetone, oxygenated water - ingredients that can be used to make explosives such as the TATP favoured by jihadists - as well as electric components, batteries and basins.
Other media reported that gas canisters were also found.
Traces of TATP -- known as the "mother of Satan" -- were found in a house where the alleged attackers in the twin jihadist assaults in Spain last month that killed 16 people were believed to have been trying to build bombs.
TATP is a homemade explosive created by mixing precise quantities of acetone, oxygenated water and sulphuric, hydrochloric or nitric acid -- all of which are easily available in high street stores.
Nail polish remover is essentially acetone, while oxygenated water is a commonly used disinfectant.
The mixture creates a coarse powder of white crystals that requires only a basic detonator to explode, triggering a huge blast of burning gas.
The Paris prosecutor's office confirmed that "elements that may be part of the composition of explosives" were found in the flat in Villejuif.
Its counter-terrorism section has opened an investigation under potential charges of "criminal terrorist association" and "possession, transportation and production of explosive substances in relation with a terrorist action by an organized gang."
France is still under a state of emergency after November 2015 terror attacks killed 130 people.
by Rory Mulholland