Four people were arrested in the Paris region Wednesday morning and France's interior minister says there were fears that they were planning an attack, NBC News reported.
French Interior Minister Bernard Cazeneuve said the four were taken in for questioning, including one man under house arrest, who was suspected to be in contact with Islamic State extremists.
Judicial and police officials, who requested anonymity to discuss the detentions, said one of the four was a woman and all were born in France. They were between 21 and 30 years old, the officials said.
A subsequent search found an unused Kalashnikov cartridge, SIM cards, USB cards and a gun for firing blanks.