A police source confirmed the new discovery in Thiais, a suburban city close to the Villejuif apartment where TATP was found Wednesday thanks to a tip from a plumber.
Police found substances that "may be used to make explosives" in the unit, Collomb said, praising the "civic reflex" of the worker.
The source specified, as cited by Reuters that TATP explosive was found in the Paris suburb of Villejuif.
The pair were arrested as they were driving a small van that belongs to one of the flat's tenants, a police source said.
Police raid a block of flats in Barking, making 12 arrests believed to be connection with the London Bridge terror attack.
A counterterrorism investigation was opened under potential charges of "criminal terrorist association" and production, possession and transportation of explosive substances "in relation with a terrorist action by an organized gang".
The Eiffel Tower and the Eurostar terminal at the Gare du Nord were evacuated amid a swoop by police.
Matchup breakdown for Ohio State
Ohio State is plenty capable of moving the football but to outscore the Sooners by a touchdown in this game is very debatable. The over/under total for the contest is listed at 64.5 points. "The big games like this, you see how physical you are".
French Interior Minister Gérard Collomb said the suspects deny any terror plans despite regular phone contacts with people in Syria.
Two men were detained Wednesday and the third man on Thursday. "But what we can see is that they..."
The unnamed man noticed chemicals on a balcony of the flat as well as a soldering iron and hot plate through the window.
France has suffered more than other European countries from Islamic extremist attacks in the last two years.
The jihadis behind the Brussels terror attacks used a highly-volatile explosive nicknamed the "Mother of Satan".
France has been under a state of emergency since IS gunmen launched a series of simultaneous raids on bars, the national stadium and the Bataclan concert hall in Paris in November 2015, leaving 130 people dead.