The suicide cell that killed 52 people in London on July 7th is not linked to those alleged to have been behind the attempted attacks on July 21st, according to a report.
The Independentreported unnamed sources saying that the initial findings of an investigation into both attacks had found no evidence of any al-Qaeda "mastermind" or senior organiser.
The investigation, which the newspaper said involved MI5, MI6, the listening centre at GCHQ and the police, reportedly found that the July 7th team worked in isolation and was radicalised by Mohammad Sidique Khan, the oldest of the four bombers.
A Metropolitan Police spokesman said that police would not comment on the report or any other speculation about the attacks.
The newspaper said police and MI5 feared the findings suggested more "self-sufficient" units similar to the July 7th cell were hiding in Britain.
The investigation reportedly concluded that the alleged plotters behind the July 21st incidents were probably "copycats", targeting Tube trains and a bus.
A counter-terrorist source told the newspaper: "The key point is the events are not connected. It appears they were self-contained, rather than being organised by some kind of mastermind.
"It is concerning that none were on the intelligence radar. There are quite probably others we do not know about out there. Over the past 10 years, we have been successfully disrupting a number of groups of people who could have carried out bombing attacks similar to those we have seen in the past few weeks.
"We can't disrupt them all. They only have to be lucky once - and they have been. At some point there will be another suicide or bombing group."
The newspaper said intelligence agencies and police had trawled through telephone and computer records, emails, forensic evidence, and investigated friends and associates to build up a picture of the suicide bombers. Investigators reportedly found that the July 7th cell did not conform to previous al-Qaeda units.