Temperatures in the section of the Piccadilly Line tunnel where rescuers are still trying to recover bodies following the Tube bombs have at times reached 60 degrees Celsius, it emerged today.
Scotland Yard's senior identification manger Detective Superintendent Jim Dickie said the extreme heat was a "significant factor" in the recovery operation close to Russell Square Tube station.
There are still an unknown number of bodies - previously believed to have been around 20 - inside the carriage of the train which was hit by one of Thursday's terrorist bombs. Rescue workers are battling horrific conditions throughout this weekend as they try to recover all of the remaining bodies within the next 48 hours.
Refrigeration units have been taken to the scene to store the remains before they are taken to a temporary mortuary at an undisclosed military site in central London.
There are still bodies at the two other Tube blast sites - at Aldgate station and Edgware Road - although it is thought the Russell Square site is the only one where they remain in situ on the train. There, the affected carriage is several hundred yards from the station, which is deep underground, around 100ft below the surface.
Only a certain number of rescuers can work inside the tunnel at any one time and the teams have to return to the surface periodically, so harrowing are the conditions.
Deputy Chief Constable Andy Trotter, of British Transport Police, warned that it would be some time before the "methodical and meticulous" recovery operation was finished.
"The search was halted overnight because of the increasingly difficult conditions but it resumed again early this morning," he said.
Mr Trotter said a meticulous forensic search was continuing at all four blast sites as part of the hunt for the perpetrators of "this ghastly crime".
CCTV footage from bus and underground stations, shops and traffic cameras was also being analysed, he said. "We know we have had successes in preventing terrorist atrocities in London but this time they got through," he said.
"But we are quite determined to redouble our efforts to keep London safe."
PA