A lecturer of a technical institute at Panvel in the neighbouring Raigad district was on Monday grilled in Mumbai for his suspected role in radicalising youths towards terror group Islamic State of Iraq and Syria (ISIS), a state Anti-Terror Squad (ATS) official said.

"The lecturer with a technical institute in Panvel was today called to the ATS office here and questioned for several hours. The lecturer had been grilled earlier too. This time he was summoned over further developments which emerged during the course of ongoing probe," an ATS official said.

The principal of the institute had also been asked to appear before the investigators today, but he did not turn up citing personal reasons.

"We will decide about the next date when the principal could appear before us," the official added. About 40 people from Kalyan, Thane and Raigad are under the ATS scanner for allegedly propagating ISIS among youngsters.

In May this year, four youths-- Arif Majeed, Shaheen Tanki, Fahad Shaikh and Aman -- from neighbouring Kalyan town had left India to visit holy places in the Middle East, but disappeared thereafter. They were suspected to have joined the ISIS. On August 26, Majeed was reportedly killed in bombing.

However, the ATS is yet to establish a direct link between those questioned so far with the four youngsters, who sneaked out of the country six months ago.

During the investigation, the agency had discovered that two Afghan nationals -- Rehman Daulati and Ahmed Rateb Husseinzade -- were persuading youngsters from Kalyan and allegedly indoctrinating them.

Also, they had flouted the Foreigner's Act, Registration of Foreigner's Act and Registration of Foreigner's Rule, police said. Further probe revealed that one Aadil Dolare, a fruit seller, was suspected to be the main person involved in brainwashing the four men from Kalyan, they said.

An FIR had been registered at the Bazarpeth police station in Kalyan against Dolare, the Afghan nationals and the manager of a hotel (in Kalyan), Govind Thappa, in the last week of September, who allowed the foreigners to check into the hotel, but did not inform the police as per norms, police added.