48-year-old Dominic Martin, the main suspect in the serial blasts in Kerala's Kochi during a prayer meet on October 29 reportedly learnt bomb-making from the internet, NDTV reported.
The report stated that Martin has claimed he spent about Rs 3,000 to make the bombs. The accused worked in the Gulf for many years and he reportedly learnt how to put together an electronic device during his stint there. He returned from the Gulf two months ago, according to NDTV's source-based report.
It adds that low-grade explosives were used in the bombs made by Martin. He reportedly assembled the IEDs at his home.
The blasts were set off at a convention centre in Kalamassery near Kochi where a prayer meeting of the Jehovah's Witnesses -- a Christian religious group that originated in the US in the 19th century -- was held on Sunday.
A few hours after that, Martin, who claimed to be an estranged member of Jehovah's Witnesses, surrendered before police in Thrissur district of the state, saying that he carried out the multiple blasts.
Before he surrendered, he posted a video on social media stating his reasons for carrying out the blasts.
By Sunday evening, a 21-member special investigation team (SIT) of the Kerala Police, headed by ADGP Ajith Kumar, was set up to probe the case.
Initially, one woman had died and 60 were injured, six of them critically, in the blasts. Subsequently, one of the six critically wounded -- a 53-year-old woman -- succumbed to her injuries. By Monday morning, the death toll rose to three with the death of a 12-year-old girl who had suffered 95 per cent burns in the incident.
Presently, 21 people are under treatment for injuries suffered in the blasts and of them 16 are in the ICU, a state Health Department bulletin said.
Of the 16, three are in severely critical condition, it said.
(with PTI inputs)