Highly explosive devices and a mobile phone as trigger were used by terrorists in Wednesday's low intensity bomb blasts that rocked the city, police said Friday.
Samples collected from the blast sites by a team of the National Security Guard from Delhi along with forensic experts from Kolkata have prima facie revealed that the explosives used were of most recent vintage, DIG, (police control) Nepal Das said.
The terrorists used mobile phone as the timer device and batteries of 9 volts which enabled the serial blasts to take place within a short span of time, he told PTI.
Also, the explosives contained ammonium nitrate and fuel oil. If the quantity of explosives were more, the impact of the blasts would have been far worse. The blasts had a lot of similarities with those which took place in other parts of the country, Das said.
He said no bomb was recovered on Friday, but search operations are still on.