Police sources in Milan said on Saturday that Bentiwaa Farida bin Bashir, a 42-year-old Tunisian, was arrested on Friday as she arrived at Milan's Malpensa airport on a flight from Tunis.
Italy said last month it had smashed the suspected recruiting network when five arrests were made in Italy and Germany. Bin Bashir was initially reported as being among those
arrested but it then emerged she was still free.
Among the people arrested in November as part of the same investigation was the suspected ringleader, Abd al-Razzaq Mahjub, an Algerian believed to have had contacts with those behind the September 11 attacks in the United States.
No charges have been brought following any of the arrests.
There was no immediate comment from bin Bashir or her representatives.
Interior Minister Giuseppe Pisanu said at the time people were being approached in Italy and then sent to camps in northeastern Iraq, where they received training from members of the Ansar al-Islam group.
Washington has described that group as its main "terrorist adversary" in postwar Iraq, where US-led troops face daily guerrilla attacks.
Police sources said on Saturday bin Bashir was suspected of playing a logistical role in the recruiting network but was not considered a combatant.