Gas canisters, electric wiring and chemicals that could be used to make explosives were among items found in the flat near Villejuif, south of the French capital, the sources said.
One of the arrested pair, 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 flat.
Police found ingredients that can be used to produce the home-made explosive TATP, commonly used in attacks by the Islamic State group (IS), a source close to the case said.
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The case is being handled by Paris anti-terror prosecutors, a judicial source said.
France has been under a state of emergency since IS jihadists attacked 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.