For the past few years,ammonium nitrate has been the common ingredient of the bombs used in most terror attacks,though different bombs have had different substances combined with the basic,easily available ingredient.
Ammonium nitrate was used in Wednesdays serial blasts too,investigations by the National Investigation Agency (NIA) and the National Security Guards (NSG) have indicated. It has replaced RDX and TNT in most blasts since 2003.
Ammonium nitrates primary use is as a fertiliser. It is readily available. In cities like Delhi,Mumbai and Bangalore,the anti-terror units of the local police have been told to keep a stock of all sales and purchases of ammonium nitrate; shopkeepers have been asked to inform the cops if anyone makes a bulk purchase, an NIA official said. Ammonium nitrate is mixed with fuel when put into a bomb,which is then triggered by a detonator,an NSG official said. Since 2003,the bombs based on ammonium nitrate have been built with a mixture of the chemical with RDX.
Ammonium nitrate bombs are usually placed in a C-shaped open wooden box holding the circuit through holes on the side for wires to pass. The explosive is essentially tightly packed ammonium nitrate,held together by fuel or nitrogen gel,metal balls and nuts for splinters,and with a timer. Such bombs went off in UP,Ahmedabad,Bangalore,Delhi,and Jaipur.