The 23-year-old sent an email threatening to blow up the Chhatrapati Shivaji Maharaj International Airport if he was not paid 'US$1 million in Bitcoin', according to an official.
The bodies of the slain personnel will later be flown to their home towns
A slip from the train led to the arrest of Shahrukh Saifi, the suspect in the Executive Express arson attack case.
The investigation team zeroed in on Shahrukh based on the documents obtained from a bag that was left abandoned on the railway track.
According to the police, they have also recovered explosives and firearms from Uttar Pradesh, Delhi and Maharashtra.
The Crime Branch wing of the Kerala police had been probing the case in which gangster Ravi Pujari is a key accused.
The ATS was formed to monitor terror activities in the coastal state and for effective pursual of terror-related cases.
During the searches, the ATS sleuths seized certain chemicals, acid bottles, sharp knives, mobile phones, hard disks and some SIM cards from the group.