LONDON - The bombs used in the terrorist attacks on London were of "military origin", says a senior French policeman sent to the city to help in what has become the biggest criminal investigation in British history.
Christophe Chaboud, head of the French Anti-Terrorism Co-ordination Unit, told the newspaper Le Monde that the explosives' military source was "very worrying".
"We're more used to [terror] cells making home-made explosives with chemicals," he said.
"How did they get them? Either by trafficking, for example, in the Balkans, or they had someone on the inside who enabled them to get out of the military establishment."
He added that the victims' wounds suggested that the explosives had been placed on the ground, perhaps beneath seats.
In key developments yesterday:
* NBC reported that British investigators told US counterparts they had found fingerprints on bomb materials, adding that at least four operatives were believed to have been involved.
* Law enforcement officials said investigators suspect the bombers congregated at the King's Cross Tube station, then set out to plant the devices, NBC said.
One train was eight minutes east of King's Cross when a bomb on it exploded. Another was eight minutes west. The third was just seconds south. And the double-decker bus in Tavistock Square was only a short walk away when the bomb aboard it - the last of four - went off.
"The coincidence of all the trains coming through here is obviously one line of inquiry we are pursuing," said Deputy Chief Constable Andy Trotter of the British Transport Police.
* The Financial Times said British police were on the verge of identifying one person they believe was involved in the attacks.
The paper, citing an unnamed European official involved in efforts to find the bombers, said progress had been made towards naming who was responsible for the bus blast.
"I think we are going to see photographs of one or more suspects being posted within days," the official said.
* The Times said forensic pathologists were paying particularly close attention to two bodies found inside the bus to see whether one might have been the bomber.
"There are two bodies which have to be examined in great detail because they appear to have been holding the bomb or sitting on top of it," a "senior police source" told the paper. "One of those might turn out to be the bomber."
* According to the Times, a single bomb maker using military-grade explosives was most probably responsible for making all the bombs used in the attacks. Similar components had been found by police at all four bomb sites, the newspaper said.
Many of the 400 extra police being drafted in to help with the inquiry will be helping analyse thousands of hours of video recordings from cameras on and around the Tube lines and the bus struck by the terrorists. Police have so far taken 2500 videotapes and are expected to examine many more.
Senior detectives said the analysis of images from surveillance cameras was the biggest closed-circuit television (CCTV) trawl ever. Detectives hope that among the tens of thousands of hours of footage will be pictures of the terrorists.
As well as examining cameras on the three bombed trains, police have been recovering every camera in the stations the trains travelled through, and cameras outside every station entrance.
The Tube bombs were on the southbound Piccadilly line and the Circle line, which means there were 40 Underground stations where the bombers could have got on board.
As well as examining cameras on shops and other businesses, the police will look at speed cameras.
A police source said of the CCTV task: "It is a massive job that is very time-consuming; it sounds impossible - but it's not."
Forensic science specialists and anti-terrorist officers yesterday continued to examine the four crime scenes for traces of the bomb and a possible suicide bomber. This includes x-raying bodies to see if any bomb parts or timing devices are embedded in them.
Sir Ian Blair, commissioner of the Metropolitan Police, described the areas of investigation as "the biggest crime scenes in English history".
James Hart, commissioner of the City of London Police, said: "We can't possibly assume that what happened on Thursday was the last of these events ... We have to be vigilant."
Magnus Ranstorp, deputy director of the Centre for the Study of Terrorism and Political Violence at the University of St Andrews, said: "Last year in Madrid, the bombers had a large amount of explosives, and looked to be preparing to launch new attacks. We have to assume that it is the case here, as well."
Dick Leurdijk, who studies terrorism at the Clingendael Institute, a Dutch research centre, offered a similar view.
"If the purpose of terrorism is to create terror, a second attack coming in the next few days would be a serious blow to the European notion of security," he said. "This looks to be the work of terrorists with an international agenda, so the attack needn't come in London, or on the subway. But every European capital is on high alert right now, and with reason. A number of people are convinced another attack is coming."
- INDEPENDENT, AGENCIES