Arif appears "highly radicalised" is likely to face action, police said.
In May this year, four youths from Kalyan-Shaheen Tanki, Fahad Shaikh and Aman Tandel, besides Arif--had left India to visit holy places in the West Asia, but they disappeared thereafter and since then were suspected to have joined the Sunni extremist group.
Arif returned early this morning and was quizzed by the NIA and Maharashtra Anti Terrorism Squad (ATS), a police officer said.
Soon after his return, Arif was made to undergo a medical examination, according to a source.
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His family friend Iftekhar Khan told PTI, "Arif's father Ejaz received a phone call from security agencies this morning saying his son is in Mumbai."
According to police, the four engineering students flew to Baghdad on May 23 as part of a group of 22 pilgrims to visit religious shrines in Iraq.
"On August 26, Shaheen Tanki called up Arif's family and told them that their son had become a 'martyr' claiming that the latter died fighting for ISIS in Syria," a family friend Ateek Khan had told reporters.
Accordingly the next day, Arif's family performed 'Janaza-e-gayabana' (prayers for the departed soul in absence of the body) in Kalyan.