Mehdi Masroor Biswas, the owner of a pro-Islamic State (IS) twitter account @ShamiWitness, who was arrested in Bengaluru on Saturday, had been under surveillance by the Central intelligence agencies for sometime but given a long rope to see whether any “real IS operative would contact him,” an intelligence source claimed.

“The fact remains that he did not travel outside, he did not recruit anyone personally nor been in touch with any person for the purpose of terrorism. We were waiting to see whether he would come into contact with anyone,” the source told The Hindu.

The source said there were other people also under similar surveillance, but action would be taken only at an appropriate time. “There are many people who propagate Maoism, and we know them. But we don’t arrest them until there is more to it,” the source said.

The National Investigation Agency (NIA), which has been closely watching the developments in the case, rendered assistance to the Bengaluru police in guiding their probe and lodging of the FIR against the 24-year-old techie.

Sources said investigation would need to be thorough to make a “watertight” case. Under the Unlawful Activities (Prevention) Act, terror outfits like the IS that have been banned by the United Nations, attract a ban automatically in India.

The investigators would need to track down the original tweets from the now-defunct account in order to support the case. “It appears that the youth was influenced by the ideology and was getting a kick by retweets and the number of followers. The probe will need to be carefully monitored. It looks like Mehdi was active in the virtual world and on his keyboard,” the sources said.

(With inputs from Varghese K. George)