[What follows is an excerpt from a report headlined FBI combs Boston crime scene for clues published this evening on the website of The Financial Times:]
Tom Thurman, a former FBI explosives specialist who was involved in the investigations of the bombing of the Pan Am flight over Lockerbie and the 1993 World Trade Center bombing, said the fact that the bombs produced white smoke indicated they were probably an improvised device. While military explosives such as C4 cause big plumes of black smoke, he said, white smoke was usually the result of a device that contained gunpowder or a commercial rock-blasting explosive such as dynamite.
Mr Thurman, now at eastern Kentucky University, said an improvised device would need to be packed into some form of container such as a pipe, which could explain the reports of extensive shrapnel wounds among some of the victims.
While the FBI, which is leading the investigation, said it was pursuing a number of leads, former security officers warned that such cases can sometimes take a long time to resolve.
[It was Tom Thurman who purportedly identified the crucial Lockerbie circuit board fragment as coming from a MEBO MST-13 timer. Posts on this blog in which he is mentioned can be accessed here.]