Were Mumbai blasts caused by human bomb? Unlikely

It's unlikely that human bombs were used in Wednesday's triple blasts in Mumbai. Vicky Nanjappa tells you why.

Mystery still shrouds the whereabouts of a suspected 'human bomb' whose body was found entangled in wires from the site of one of the three blasts that rocked Mumbai on Wednesday evening.

The police has not yet divulged any information on this man, about whom Union Home Secretary RK Sigh speculated on Thursday that he could be a possible 'suicide bomber'.

While this is an angle that definitely needs to be explored, the question is whether after finding traces of ammonium nitrate from all the three blast sites, is it still possible to come to the conclusion that it was a human bomb which carried out the explosions?

Before we delve into this, there is a need to understand the difference between a human bomb and a suicide bomber.

The concept of suicide bomber is relatively old and was first used by the Japanese during World War II. A suicide bomber is one who carries a bomb with him and attacks a target, thus killing himself/herself.

The human bomb, however, is a concept introduced for the first time during the assassination of former prime minister Rajiv Gandhi at Sriperumbudur in Tamil Nadu in 1991.

Usually in the case of a human bomb, the explosive is concealed in the body, usually RDX, apart from electrical detonators which is powered by a 9-volt battery. The detonator explodes once it heats up.

Speaking of the Mumbai serial blasts now, it is unlikely that the bomber would have carried a bomb on his body. The reason being that, unlike RDX, ammonium nitrate requires a container.

In the case of RDX a cloth or paper is sufficient to conceal the bomb. While RDX acts as an explosive on its own, ammonium nitrate does not become an explosive unless it is mixed with fuel oil which is known as ANFO.

Dr P Chandrasekharan, who led the forensics team during the probe into the Rajiv Gandhi assassination case, says that ammonium nitrate, unlike RDX, needs to be put into steel tubes of different diameters.

If a person carries it on his body it becomes very bulky. Terrorists would usually avoid it since it is easily traceable and could even be visible to the naked eye as the equipment is very bulky, Professor Chandrasekharan points out.

"In the case of human bombs, terrorists would always prefer the use of RDX which is semi-solid and easier to shape according to the body type. Moreover, RDX shaped into the body is not easily detectable unless the person is very closely frisked," he adds.

"RDX, however, has proven to be a more powerful explosive but the usage is low in today's world of terror since it is not easily available unlike ammonium nitrate which still can be purchased off the shelf. RDX, compared to ammonium nitrate mixed with fuel oil, is three times more powerful," he says.

"RDX has a velocity of detonation of 26,000 per second as opposed to ammonium nitrate mixed with fuel oil which has a VoD of 10,700 per second. RDX needs an electric detonator apart from two switches -- one for arming and the other to initiate the device," he also adds.

"Hence, in the case of Wednesday's triple blasts in Mumbai, if investigators pick up the fragments of the tube used for the bombs, they can infer that it is not a human bomb. Moreover, a human bomber will usually have a severed head and his limbs are separated, and in this case it does not appear to be so," he adds.