The suicide bomb plot hatched in Yorkshire

The terrorists responsible for the Tube and bus attacks in London have been revealed as home-grown suicide bombers.

The four young British men, all thought to be of Pakistani origin, are believed to have blown themselves up with rucksack bombs on Thursday, killing at least 52 people.

Three of the bodies of the terrorists responsible for what was the first suicide bombing in western Europe have been identified, while a fourth is thought to be among the remains in the wreckage on the Piccadilly line between King's Cross and Russell Square.

Police raids at six homes in north Yorkshire yesterday also led to one arrest. But senior security sources warned last night that they suspected al-Qa'ida planners ­ bomb-makers and organisers ­ were still at large and further suicide bombings were likely. The four men, including one teenager, all from Leeds and Dewsbury in West Yorkshire, were not considered Islamic extremists and were not thought to have significant links with terrorism.

The realisation that British nationals are prepared to make suicide attacks has transformed the way the country will have to view security.

"What we considered normal has changed forever," said a senior security source.

Security measures at all public places will have to be rethought. Tough new security laws are also expected to be introduced to try to combat the threat.

Anti-terrorist officers raided houses in Leeds and Dewsbury where they found a "bomb factory" believed to belong to at least one of the terrorists.

Explosives were also found in a car at Luton railway station, which is thought to have been used by the bombers to drive from Leeds on Thursday.

Police searched Colenso Mount in Leeds, the home of Hasib Hussain, believed to be responsible for the bomb on the No 30 bus that blew up in Tavistock Square. They also raided Colwyn Road in Leeds, the home of Shahzad Tanweer, believed to be responsible for the Aldgate blast.

It is understood that 19-year-old Hussain's driving licence and credit cards were found in the wreckage of the No 30 bus. The bus bomber is thought to have failed to get on a Northern line train so boarded a bus instead. For some reason he detonated his bomb nearly an hour after his fellow terrorists had exploded theirs.

Tanweer, age 23, the man believed to have been responsible for the Aldgate blast, was seen by police officers on CCTV footage. Scotland Yard said the footage of the four men at King's Cross station shows them with their rucksack bombs minutes before the attacks.

Tanweer and Hussain's houses were among six raided by West Yorkshire Police. The men are known to have been missing since last week. Tanweer, who was said by neighbours near his home in the Beeston area of Leeds, to have been a university graduate and keen local cricketer, had not been at home since last week, which had been a cause of concern for his father Mohammed, who runs a chip shop near the family home.

His friend, Azzy Mohammed, said: "We played cricket together and I could not imagine him doing anything to hurt anyone as he has a very strong family."

Hussain, from the Holbeck of Leeds, is understood to have been the subject of attempts at discipline by his parents after becoming difficult to control in his adolescence. But he became devoutly religious 18 months ago and is believed to have gone to London last week, since which time he has not been seen or contacted,despite the efforts of his older brother.

Detectives evacuated 500 homes before carrying out a controlled explosion in the Burley district of Leeds.

The breakthrough in the investigation came at 8pm on Monday when detectives found a CCTV picture of the four bombers at King's Cross station 20 minutes before they blew themselves up.

But a senior security source warned last night: "We have not got the plotters or planners. Al-Qa'ida methodology is to put someone into the country ­ they do the preparation and they are out the door."

He said the fear remained that whoever helped the four bombers has recruited and trained other British suicide attackers. "How many other clean skins are waiting in the wings?" he said.

Only one of the three identified suicide bombers had any known connection to al-Qa'ida suspects, and it was a very low level of association, according to security sources.

Hours after the Leeds raids, police evacuated Luton railway station and car park as they recovered two vehicles, one of which was later found to have explosives inside.

Deputy Assistant Commissioner Peter Clarke, head of Scotland Yard's anti-terrorist branch, said: "The investigation is moving at great speed.

"We are trying to establish the movements of the suspects in the run-up to last week's attack and specifically to establish whether they all died in the explosions."

Assistant Commissioner Andy Hayman, leading the police hunt, said the bombings were the work of "extremists and criminals".

Tony Blair issued a defiant statement saying: "Together, our modern, diverse and tolerant country will ensure the terrorists fail in their attempts to destroy the way of life we all share and value."

The final death toll from Thursday's attacks is expected to rise above 52, with police assigning family liaison officers to more than 70 families.

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