Kochi (Kerala), Oct 29 : The investigation into the multiple bomb blasts in Kerala's Kalamassery Convention Centre on Sunday has revealed that an Improvised Explosive Device (IED) kept in a tiffin box was used to trigger the explosion, said sources. One person was killed and 40 were injured in the blasts. Among the injured, the condition of seven persons was critical. Kerala DGP Sheik Darvesh Saheb ruled out the initial reports of the explosion taking place due to an electric short circuit and confirmed that the explosion was a bomb blast. Sources have also confirmed that it was an act intended to create terror. About 2,000 people were gathered for prayers at the convention centre at the time of the blast. A four-member team from the National Intelligence Agency (NIA) from Kochi was at the spot. Sources confirmed that the NIA team from New Delhi had left for Kerala to take over the investigation. According to police, multiple explosions were reported from the spot where the meeting of Jehovah Witness Believers was held. The blasts had occurred at around 9 a.m. The hall was sealed and Kerala Police Anti-Terror Squad was at the site. Jehovah Witnesses are a group of Christians who do not identify themselves as Protestants. The Jehovah Witness Convention is an annual gathering where large assemblies called Regional Conventions take place which are held for three days. The event had started last Friday and it was supposed to end on Sunday, according to sources. All injured have been shifted to the Government Medical College Hospital in Kalamassery, sources said. Kerala Chief Minister Pinarayi Vijayan described the incident as "very unfortunate".All aspects will be deeply probed, he underlined. CM Vijayan, who is in Delhi attending his party meeting, has deputed state Cooperation Minister V.N. Vasavan. Vasavan reached the site and told the media that it was a very unfortunate incident and details of the blast were not ascertained as yet. CPI (M) State Secretary M.V. Govindan says the terror angle should be looked into in connection with the bomb blast incident. The police sources said the deceased was a woman and her identity was yet to be ascertained. /IANS