The London bombings were carried out with military explosives, European security officials familiar with the probe have said.
'The explosives appear to be of military origin, which is very worrying,' said Christophe Chaboud, head of the French Anti-Terrorism Coordination Unit and one of five top officials sent by Paris to London immediately after Thursday's attacks.
'We're more used to cells making home-made explosives with chemicals. How did they get them?' he said in an interview with Le Monde newspaper. 'Either by trafficking, for example, in the Balkans, or they had someone on the inside who enabled them to get them out of a military establishment.'
London police, have admitted the bombs contained less than 10 lb. (4.5 kg) each of 'high explosives' and were small enough to be carried in rucksacks. By comparison, the 10 bombs that blew apart four commuter trains in Madrid last year weighed about 22 lb. (10 kg) each. The explosive in that case was Goma 2 Eco -used in quarrying.
Meanwhiule, Israel police now claim that the explosives were materially identical to those used by two British Muslim suicide bombers Tel Aviv more than a year ago.