As painstaking forensic work continues at the sites of Thursday's four bomb explosions, London was making earnest efforts to get back to some sort of normality today.

Search teams are continuing with the attempt to recover the bodies of victims, which are in the wreckage of the train at Russell Square, although a number of bodies have now been removed.

Fingertip searches are also being carried out for clues in the hunt for the identity of the bombers.

The police investigation is now concentrating on King’s Cross station, the only station through which all the targeted tube trains passed. It is believed that the bombers may have assembled at King’s Cross, before boarding different trains with their bombs.

Police will also interview survivors from the bus blast. There had been speculation that the bus explosion was caused by a suicide bomber, although other theories have now been put forward, including suggestions that the blast may have been targetting people evacuated from tube trains or that the bomb exploded accidentally while the bomber was travelling to another target.

A passenger on the bus, Richard Jones, told ‘The Sun’ newspaper last week that he saw a man continuously fiddling with something in a bag. Mr Jones told The Sun that the man looked ‘nervous’ and was “continually diving into his bag, rummaging round and looking in it.” Mr Jones got off the bus just before it exploded.

It is understood that police are almost certain that suicide bombers did not carry out the attack. The state of alert in Britain has now been raised to “severe specific” over fears that the bombers may strike again.

Three people were arrested at Heathrow airport yesterday under anti-terrorism laws, but there has been no link made between them and the London attacks. They were later released without charge.

Police have received almost 1,700 calls to the anti-terrorist hotline since Thursday’s attacks. They are urging anyone with video, photographic or mobile phone footage from anywhere around the scenes of the explosions to e-mail them to police at: images

Those with information should contact the anti-terrorist hotline on 0800 789 321.

However, police and politicians are urging the public to return to work, stressing that London is now “open for business again”.

Deputy Chief Constable Andy Trotter from British Transport Police stressed that police forces and security services were working together to keep London safe and that the city had defeated terrorists in the past and would continue to do so.

Many employees who were given the day off on Friday returned to work for the first time on Monday. A number of schools, which were closed on Friday, also re-opened on Monday.

London transport has almost completely returned to normal, with many buses and trains operating as usual. However, diversions are in place around the sites of the four explosions.

London Mayor Ken Livingstone took the Tube to work on Monday, in an attempt to encourage people to do the same.

(KMcA/SP)