"It was a timely wake-up call. We are lucky to have busted the cell. The success came after strenuous tracking and shadowing of suspects over a considerable period. There could still be some more sleeper cells around, we have stepped up vigil," said a senior officer.
He, however, refused to divulge more details of how Irshad Khan and his engineering student-nephew Abdul Rahman from New Delhi were arrested from suburban Selaiyur on November 27.
Imran alias Asif, a most wanted member of terror outfit IM, who had arrived in Chennai with Irshad from New Delhi and is suspected to have provided logistical backup and financial help to IM modules, has disappeared.
Three more engineering students were arrested along with the duo but were released after being grilled. Meanwhile, Irshad Khan and Abdul Rahman were taken to Delhi for further investigation.
Sources reveal that Irshad and two of his accomplices visited 'two or three very crowded areas of Chennai during peak hours' for a couple of days before they were picked up.
"They were not there for shopping, obviously, so what were they doing there? We suspect they were checking out possible targets," said the source.
"They (terrorists) had been keeping away from Tamil Nadu, particularly Chennai, because of efficient and experienced police networks, both state and central, and also because they would stand out in a Tamil crowd," said an officer.
Earlier, analysis revealed that Bangalore and Hyderabad were also a possible target for terrorists.