At 12:55 pm on March 1, as the popular Rameshwaram Cafe in Whitefield was packed with customers, there was a low-intensity explosion, leaving people terrified, injuring nine, and prompting a multi-agency probe. 42 days later and a chase which involved the participation of security agencies across states later, the NIA on Friday arrested Mussavir Hussain Shazib (30) the man who allegedly planted the bomb, and Abdul Matheen Ahmed Taahaa, the man that allegedly masterminded the explosion from a hotel in the West Bengal’s New Digha.

The first clue that investigators found immediately after the blast was CCTV footage of Shazib leaving a bag that contained the IED device near the restaurant’s cash counter. As they traced his movements, they saw him boarding a Bangalore Metropolitan Transport Corporation(BMTC) bus that took him outside of the city limits and then again in a Karnataka state government bus in Tumakuru.

Shazib was next spotted at a bus stand in Ballari, speaking to two others. “Two unreserved seats were occupied by individuals who alighted at the Ram mandir circle and central bus stand in Kalaburgi late on March 1,” an NIA officer said.

Simultaneously, a cap left behind by Shazib was another clue that investigators honed in on, discovering that it was bought in a mall in Chennai. This detail, NIA officers said, helped link Shazib and Taahaa. They found that the two had stayed in Tamil Nadu in January and February when preparing for the blast, one officer said.

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The officer said that the central agency was able to trace the movements of the two accused from Bengaluru to north Karnataka, to Mumbai and then to Ratnagiri in Maharashtra.“It appears from there they went to Nellore in Andhra Pradesh and then to Chennai. After staying in Chennai for a few days, they went to Assam and finally reached West Bengal a few days ago,” the officer said.

NIA officials said that a team led by inspector general of police, Santosh Rastogi, led the manhunt and coordinated with anti-terror units of Karnataka, Kerala, Uttar Pradesh, Telangana and West Bengal.

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Investigations also revealed that the two men rented a room at Hotel Paradise in Lenin Sarani in central Kolkata on March 13, checking out the next day. The documents they used carried the named Y Shahnawaz and Anmol Kulkarni, which investigators believe are fake. On March 26, in raids across 18 locations across three states, the NIA arrested Muzammil Shareef, who has since been charged of helping with logistics. 17 days later, at 2 am, Shazib and Taha, in a joint operation with the West Bengal Police, Shazib and Taha were in police custody.

(With inputs from Arun Dev and Joydeep Thakur)