Those brought into the mainstream include well-educated people like a young couple, both post-graduates in pharmacy, an aeronautical engineer and an IT professional, he said.
The deradicalisation is done to bring back to normal life persons who had strayed in the name of 'jihad', a senior official of the ATS said.
He said all these people, including eight women, had come in contact with their handlers via social networking sites and were radicalised online.
They were on the verge of joining the terror outfit ISIS or planning to work for it, but the law-enforcement agencies silently monitored their activities and successfully brought them back to the normal life, he said.
The ATS approached the family members of these people, their community's spiritual leaders and counsellors were also roped-in. After continuous efforts for more than two months in each case, all these people were deradicalised and now they have been brought back into the mainstream, he said.
Among the many other initiatives of tackling terrorism post the 26/11 Mumbai terror attack, one of the important programmes of the ATS was to keep a close watch on the online activities of young minds of the minority community, he said.
A young couple, who completed their post-graduation in pharmacy, got radicalised online following which the duo crossed the country to join the terror outfit. But, the law enforcement agencies, which were keeping a watch on them, brought them back successfully, he said.
"We have deradicalised these people and are also helping them in leading a normal life. But, we also monitoring their activities constantly because there could be some attempts from the other side to trap them again," the official said.
In 2011, four men from Kalyan township in the adjoining Thane district left the country in the name of pilgrimage and went to Iraq allegedly to join the ISIS. All of them were allegedly radicalised for jihad by their handlers, according to police.
Considering this as alarming, the law enforcement agencies became more vigilant on the online activities.
In December 2015, the ATS identified a Pune-based girl, who was indoctrinated by an ISIS sympathiser. During investigation it was found that the girl had decided to leave the country and join the terror outfit, according to police.
In an attempt to bring back these people, the ATS, with the help of the government, has taken some important steps.
These include offering training for suitable jobs and small loans with the help of banks under schemes of the Ministry of Rural Development to start their own business, so that they can live with honour and dignity, the official said.
"It is our duty to bring them on the right track by counselling and all other efforts of deradicalisation," Maharashtra's ATS chief Atulchandra Kulkarni told PTI.
Apart from this, the ATS is maintaining a strict vigil to avert any kind of terror-related incidents and activities of sleeper cells on the field. We are also providing training to our officials to update their knowledge to tackle terrorism, Kulkarni said.
"We are also translating some important books about terrorism, like of Al Qaida, ISIS, into Marathi, so that our men get an idea of the latest trends (of how to tackle such terror activities)," he said.
The ATS has modern equipment, weapons, gadgets and "we are capable enough to handle any kind of eventuality," he claimed.
In the next two-three months, the agency is expected to get more equipment from the government worth around Rs 15 crore. "These all will help in building our capacity," the ATS chief said.
The financial capital was attacked by 10 terrorists of Pakistan-based outfit Lashkar-e-Taiba, who came here by the sea route, on November 26, 2008.
In the mayhem that followed for the next three days 166 people, including 18 police officers and two NSG commandos, were killed.