Deep underground at the scene of one of the four bomb blasts, the police and other emergency services were continuing to work in difficult conditions last night to remove up to 20 bodies still trapped among the wreckage of a Tube train.
Human remains and potentially crucial forensic evidence are still inside the carriage of the Piccadilly line train, which is about 500 yards from Russell Square station deep inside the enclosed Tube tunnel.
Sir Ian Blair, the Commissioner of the Metropolitan Police, said the task was "a very long job, and a job of extraordinary horror" for his officers.
Fumes, rats, the risk of poisoning from asbestos, stifling heat and the threat of the tunnel and carriage collapsing have all seriously hampered the recovery operation and made life near impossible for emergency workers at the scene.
A senior British Transport Police officer said it was "carnage" inside.
The police said their first priority had been to get all the bodies out of the train so that detailed forensic examination of the carriages could begin in earnest.
The British Transport officer said the extensive damage to the tunnel - which is at risk of collapse - and the train itself, meant it might have to be examined in situ or even dismantled before it could be looked at properly by forensic experts.
One option under consideration is to detach four or five of the carriages and tow them away to enable emergency workers to have better access to the front carriage, which was where the bomb detonated.
It is a massive logistical challenge for police and London Underground's engineers and it is likely to be several days, if not weeks, before the affected section of the Tube line is reopened.
"The priority at this stage is to recover the bodies from the scene - and they are very difficult scenes, particularly at Russell Square," a senior police source said.
"The carriage is some 500 yards into the tunnel. The conditions are very, very difficult. It is a very bad scene down there."
Andy Trotter, Deputy Chief Constable of British Transport Police, said: "There are no living people in there and the challenge is now to remove the dead."Reuse content