Kerala explosive devices likely triggered with phone signal

NEW DELHI: The four bombs used to target a Jehovah Witnesses congregation in Ernakulam, Kerala were radio frequency-activated improvised explosive devices (IEDs) packed with low-grade explosives used in firecrackers, and had petrol pouches placed next to them for incendiary effect.
Sources connected with the post-blast investigation said the IEDs were triggered by a radio-frequency based mechanism, possibly a mobile phone signal.The preliminary assessment is that the bomber may not have been too far from the site at the time of the blasts; a source said the distance could be no more than 300-400 metres.
The IEDs were packed in jute bags and planted along with plastic pouches containing around a litre of petrol each. The bomber took care to place the IEDs and petrol pouches under separate chairs covered with cloth, so as to trigger a fire at the convention centre where over 2,000 people had gathered for prayer. An officer told TOI that plastic chairs were avoided as they would melt in the fire and not contribute to the incendiary impact that the bomber was looking to create to maximise the damage and casualties. No shrapnel appears to have been packed into the IEDs.

A source said that the nature and composition of the IEDs do not point to an expert bomb-maker but an amateur who learnt how to put together the IEDs from manuals available on the internet. The findings so far seem to confirm the claims of Dominic Martin – the main suspect in the case who owned up to the blast in a social media post and surrendered before the police – that he had assembled and planted the IEDs as he felt the Jehovah Witnesses’ teachings were “highly anti-national“.

Teams of the NIA and NSG, which reached the site Sunday, have collected bomb traces for a detailed forensic analysis. A preliminary report pointing to use of a radio-controlled IED (RCIED) will be shared with the Union home ministry.

The trigger for an RCIED is controlled by a radio link. The device is constructed so that the receiver is connected to an electrical firing circuit and the transmitter operated by the perpetrator at a distance. A signal from the transmitter causes the receiver to trigger a firing pulse that operatesthe switch. An RCIED can be triggered from cell phones, handheld remote control transmitters, car alarms, wireless door bells, pagers and portable two-way radios.
Watch Kochi blast update: ‘Placed bomb, as I was upset with Jehovah’s Witnesses’, claims Dominic Martin