A source briefed on the investigation told CNN the suspected attacker appears to have arrived in Europe on the Italian island of Lampedusa this September.
Separately, the source said that chatter in the last couple of weeks had raised concern within French security services that churches in France could be attacked.
The Italian interior ministry said Brahim Aouissaoui is Tunisian and was identified by Italian police in the southern city of Bari on Oct. 9.
Authorities gave him seven days’ notice to leave the country. He was not directly accompanied to the border as he didn’t have any previous criminal records, and was not reported by Tunisian authorities as a potential terrorist.