Explosive used in bombs 'was of military origin'

The bombs used in Thursday's terrorist attacks were of "military origin", according to a senior French policeman sent to London 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 Le Monde newspaper that the explosives used in the bombings were of "military origin", which he described as "very worrying". " We're more used to 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, which were "not heavy but powerful", had been placed on the ground, perhaps underneath seats.

Up to 400 extra police are being drafted in to help with the bombing inquiry. Many of the additional officers will be helping with analysis of thousands of hours of video recordings from cameras on and around the Tube lines and bus struck by the terrorists. Police have so far taken 2,500 videotapes and are expected to examine many more during the inquiry.

Senior detectives said that the analysis of images from surveillance cameras was the biggest CCTV trawl ever. Scotland Yard was renting extra video suites to view the tapes. Detectives are hoping that among the tens of thousands of hours of footage will be pictures of the terrorists.

As well as examining cameras on the three Tube trains hit in the blasts, police have been recovering every camera in the stations that the trains travelled through, and cameras outside the entrance of every station. The Tube bombs were on the southbound Piccadilly line and the Circle line, which means that there were 40 Underground stations where the bombers could have got on board.

As well as examining cameras on shops, banks, and other businesses, the police will also look at speed cameras. The camera on board the No 30 bus that was blown up in Tavistock Square is thought to have been faulty.

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." Between 200 and 400 extra officers from the Metropolitan Police are being deployed on the investigation. This comes on top of the 400 officers in the anti-terrorist branch and many of the 800 in the Met's Special Branch.

The important role that CCTV can play in a criminal investigation was highlighted in the case of David Copeland, the "nail bomber" who staged attacks in Soho, Brixton and Brick Lane, east London. A team of police officers had 26,000 hours of surveillance footage from the dozens of cameras in Brixton, south London. They spent 24 hours a day scrutinising busy street scenes in their effort to spot the attacker.

The first sighting of the bomber was made from cameras filming the doorway of an Iceland food store. Copeland was identified by his boss and a cab driver after police released an image taken on the day he planted his first bomb in April 1999.

Forensic science specialists and anti-terrorist officers were continuing yesterday 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, which could be vital clues, are embedded in them. It remains unclear if a terrorist died in the bus bomb, which went off an hour after the Tube explosions.

Detectives are checking all the victims from the bomb scene. An anti-terrorist source said they had recovered useful pieces of evidence, but were keeping an open mind as to whether a suicide bomber had been involved. Sir Ian Blair, commissioner of the Met, described the areas of investigation as "the biggest crime scenes in English history".

James Hart, commissioner of the City of London Police, added: "We can't possibly assume that what happened on Thursday was the last of these events ...We have to be vigilant."

Start your day with The Independent, sign up for daily news emails
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

Day In a Page

Woman who was sent to three Nazi death camps describes how she escaped the gas chamber

Auschwitz liberation 70th anniversary

Woman sent to three Nazi death camps describes surviving gas chamber
DSK, Dodo the Pimp, and the Carlton Hotel

The inside track on France's trial of the year

Dominique Strauss-Kahn, Dodo the Pimp, and the Carlton Hotel:
As provocative now as they ever were

Sarah Kane season

Why her plays are as provocative now as when they were written
Murder of Japanese hostage has grim echoes of a killing in Iraq 11 years ago

Murder of Japanese hostage has grim echoes of another killing

Japanese mood was against what was seen as irresponsible trips to a vicious war zone
Syria crisis: Celebrities call on David Cameron to take more refugees as one young mother tells of torture by Assad regime

Celebrities call on David Cameron to take more Syrian refugees

One young mother tells of torture by Assad regime
The enemy within: People who hear voices in their heads are being encouraged to talk back – with promising results

The enemy within

People who hear voices in their heads are being encouraged to talk back
'In Auschwitz you got used to anything'

'In Auschwitz you got used to anything'

Survivors of the Nazi concentration camp remember its horror, 70 years on
Autumn/winter menswear 2015: The uniforms that make up modern life come to the fore

Autumn/winter menswear 2015

The uniforms that make up modern life come to the fore
'I'm gay, and plan to fight military homophobia'

'I'm gay, and plan to fight military homophobia'

Army general planning to come out
Iraq invasion 2003: The bloody warnings six wise men gave to Tony Blair as he prepared to launch poorly planned campaign

What the six wise men told Tony Blair

Months before the invasion of Iraq in 2003, experts sought to warn the PM about his plans. Here, four of them recall that day
25 years of The Independent on Sunday: The stories, the writers and the changes over the last quarter of a century

25 years of The Independent on Sunday

The stories, the writers and the changes over the last quarter of a century
Homeless Veterans appeal: 'Really caring is a dangerous emotion in this kind of work'

Homeless Veterans appeal

As head of The Soldiers' Charity, Martin Rutledge has to temper compassion with realism. He tells Chris Green how his Army career prepared him
Wu-Tang Clan and The Sexual Objects offer fans a chance to own the only copies of their latest albums

Smash hit go under the hammer

It's nice to pick up a new record once in a while, but the purchasers of two latest releases can go a step further - by buying the only copy
Geeks who rocked the world: Documentary looks back at origins of the computer-games industry

The geeks who rocked the world

A new documentary looks back at origins of the computer-games industry
Belle & Sebastian interview: Stuart Murdoch reveals how the band is taking a new direction

Belle & Sebastian is taking a new direction

Twenty years ago, Belle & Sebastian was a fey indie band from Glasgow. It still is – except today, as prime mover Stuart Murdoch admits, it has a global cult following, from Hollywood to South Korea