Mumbai, Oct 8: One of the 11 Pakistanis involved in the July 11 serial train blasts had come here exclusively to offer his expertise for making bombs which were subsequently used to strike terror in suburban locals, investigations by the Anti-Terrorism Squad have revealed.
The bomb expert assembled the bombs using RDX, ammonium nitrate and quartz timer in pressure cookers at the residence of accused Mohammed Ali in Shivaji Nagar slum in north east Mumbai, ATS sources said in Mumbai.
Pressure cookers were used strategically in the blasts as they cause high intensity explosions and are compact in size, they said.
The core of the cookers comprised a lump of RDX placed in the centre surrounded by ammonium nitrate. A detonator comprising a quartz timer was placed over the explosives to trigger the explosions, sources said.
Two to two-and-a-half kg of RDX, four to five kg of ammonium nitrate and a quartz timer were kept in a five-litre pressure cooker to cause the seven explosions, which killed nearly 200 persons and injured over 600, according to Mumbai police commissioner A N Roy.
"The compression of all these materials into a pressure cooker gave a high intensity to the explosions," the source said.
Investigations have also revealed that the mastermind of the blasts, Faisal Sheikh was an expert in radio sensitive, remote sensitive and light sensitive detonators, the sources said. In a light sensitive device, the detonator is triggered off due to fluctuations in the intensity of light and the blast occurs in 19 minutes, they said.
While speaking to reporters last week, Roy said the seven bombs were assembled at Mohammed Ali's residence in Shivaji Nagar between July 8 and 10 and transported to Faisal Sheikh's residence in suburban Bandra.
RDX used in the blasts was brought from Pakistan by one Ehsamullah while the ammonium nitrate and cookers were procured locally, he added.
Sources added that the specialist who assembled the bomb did not play any role in the planting of bombs and fled soon after the blasts.
Eleven Pakistanis are suspected to be involved in the conspiracy out of which two have died after the blasts. Abu Osama was killed in an encounter in Central Mumbai on August 22, 2006 and Salim, a suspected planter died in the blast as he was unable to get down from the crowded coach.
Five Indians involved in planting the bombs have already been arrested by police and are on the lookout for two more.