As of now, there is no reason to believe that suicide terrorists wereinvolved. While there are as yet no indicators of the likely trigger mechanism,there are only three possibilities---a mechanical timer, a chemical timer and amobile telephone. Chemical timers of US origin given to Pakistan during the1980s were used in the Mumbai blasts of March,1993. In the Coimbatore serialblasts of February 1998, mechanical timers of local improvisation were used.Mobile telephones, which were reportedly used in the Madrid train blasts ofMarch, 2004, by pro-Al Qaeda Salaqfi terrorists, have not so far been usedin India for serial blasts. They provide a remotely controlled mechanism forwell-timed explosions within a narrow time frame as we witnessed on July 11. Precision timing is generally difficult to achieve with mechanical and chemicaltimers. A wider time span would be required.