Faulty bombs imply sloppiness or old explosive

LONDON - Poor construction, careless transportation or use of explosives that were past their "shelf life" could explain why four bombs failed to explode properly on London's transport network overnight, experts said.

The devices triggered only small blasts on three underground trains and a bus in what appeared to be a failed attempt at a carbon-copy of attacks, blamed on al Qaeda-style Islamist militants, that killed 56 people on July 7.

This time, no one was killed and only one person wounded.

Witness reports of sounds like bursting balloons or popping corks suggested that the detonators may have gone off but failed to ignite the charge, security analysts said.

"It could be they weren't constructed properly, it could be the explosives exceeded the age of their usefulness, or it could have been just sloppy handling," said Jim Ludwiczak, president of Kentucky-based Blasting and Mining Consultants.

He said the explosives used in both the detonator and the charge would have had a "shelf-life", beyond which they become unreliable.

The detonator, typically consisting of a pencil-sized blasting cap with a small amount of highly reactive explosive, would have to be in intimate contact with the charge for the bomb to go off properly.

"If the detonator slips out of the explosive, then the detonator goes off and the explosive won't," Ludwiczak said.

Police refused to be drawn on possible links with the deadly attacks two weeks ago in which four British Muslims blew themselves up and killed 52 morning rush-hour travellers.

But analysts saw two main scenarios.

Either the latest attempt was the work of "imitative amateurs" intent on mounting copycat bombings.

Or it could be a follow-up strike by the same group behind the first attacks, showing it had more operatives at large -- possibly would-be suicide bombers -- and was capable of acting despite the highest security in the British capital for years.

Security analysts said the unexploded devices would present police with a treasure trove of evidence.

"We've got intact bombs. That is forensic El Dorado," Crispin Black, director of London-based consultancy Janusian Security Risk Management, told Britain's Channel Four news.

In upbeat comments to a news conference, London police chief Ian Blair said: "This may represent a significant breakthrough, in the sense that there is obviously forensic material at these scenes which may be very helpful to us."

When 10 bombs exploded aboard four packed commuter trains in Madrid in March 2004, killing 191 people, police obtained their first vital leads from three bombs that failed to explode and were able to make their first arrests almost immediately.

"It should give them a wealth of information about the explosives used, how the bomb was put together, what components were used on it," Ludwiczak said. Some components may carry serial numbers that could help trace their origin.

Police would also be looking for fingerprints, fibres and DNA evidence on the bombs and the bags in which they were carried, as well as examining witness reports and security camera footage to locate suspects who fled the scenes.

- REUTERS