El-Bakroui, who reportedly carried out the attack at Zaventem airport Tuesday, was deported by Turkey earlier, the sources said on condition of anonymity.
Turkish President Recep Tayyip Erdogan said Wednesday that Turkey deported one of the attackers involved in Tuesday’s Brussels explosions in June 2015.
Without naming the suspect, Erdogan said Belgium was warned that the attacker captured in Turkey's southeastern Gaziantep province in 2015 was a foreign militant.
At least 31 people were killed and more than 100 others were injured in multiple explosions at Zaventem airport and a metro station in Brussels Tuesday morning.
According to Belgian media, two suspected suicide bombers were involved in the airport blast, identified as brothers Khalid and Ibrahim el-Bakroui.
A news agency linked to Daesh claimed responsibility for the Brussels attack.