Britain said yesterday it was "getting to the bottom" of a militant cell behind last week's failed attacks, amid tight security ahead of the anniversary of London's July 2005 suicide bombings.
The cautiously upbeat assessment came after Australian police searched two hospitals and questioned five doctors over the London and Glasgow attacks, after arresting a suspect earlier in the week.
Although Britain has lowered its national threat level from "critical" to "severe" after rounding up eight suspects, police remain on high alert and will be out in force for this weekend's start of the Tour de France cycle race in London.
Aweek after the London attacks -- followed last Saturday by an attack on Glasgow airport -- Prime Minister Gordon Brown voiced satisfaction with progress in the probe, which has seen eight suspects detained so far.
"From what I know, we are getting to the bottom of this cell that has been responsible for what has happened," Brown told BBC television, after speaking to Australian Prime Minister John Howard about the latest developments. "I want us to be able to work more closely with foreign authorities to deal with this security menace," he added.
Londoners have spent a jittery week since the latest attacks, and nerves will no doubt be tested on Saturday, the second anniversary of the July 7, 2005 suicide bombings on London's transport network that killed 52.
But progress in the investigation has been swift, with arrests both in Britain and Australia.
In Sydney on Friday, authorities said that officers had raided hospitals in the Western Australian cities of Perth and Kalgoorlie and briefly quizzed four Indian doctors who had previously worked in the British health system.
Federal Police commissioner Mick Keelty said a fifth doctor, reportedly an Indian working in Sydney, was questioned in New South Wales as the Australian investigation stretched into a third state.
Australia first entered the probe when Indian hospital registrar Mohammed Haneef, 27, was arrested in Brisbane, Queensland on Monday as he allegedly tried to leave the country on a one-way ticket.
He remains in custody but has not been charged. A court late Thursday granted police permission to hold him for an extra four days as the investigation broadens.
Haneef, who worked in Liverpool before finding work in Australia last September, is related to two of the medics held in Britain: Kafeel Ahmed, also known as Khalid or Khalim Ahmed, and his brother SabeelAhmed, reports say.
Kafeel Ahmed was reportedly one of two occupants of a burning and fuel-laden Jeep that was
rammed into Glasgow airport's main terminal last weekend and was badly burned in the incident.
Unconfirmed media reports in Britain said Ahmed and the other man allegedly in the car, Bilal Abdulla, an Iraqi, left a suicide note to explaintheattack.
The Ahmed brothers had also unsuccessfully applied for jobs in Western Australian hospitals in recent years, but were knocked back due to insufficient qualifications, the Australian Medical Association revealed.
A senior Scotland Yard counterterrorism officer is in Australia to help with the investigation, as her colleagues in Britain race against time to question six of the suspects held in a London police station.
Meanwhile British police have stepped up security for the Tour de France, which gets under way on Saturday after a formal opening ceremony Friday in London's central Trafalgar Square.
British newspapers said detectives are probing the role Al-Qaeda might have played in the botched attacks, in which two Mercedes cars packed with gas canisters and nails were discovered in London a day before the Jeep rammed Glasgow airport.
Indian Prime Minister Manmohan Singh meanwhile offered Brown help in the probe, but urged people not to jump to conclusions over the nationalities of the suspects.
"We offered them all possible help in dealing with this, but I think labelling Indians as terrorists, Pakistanis as terrorists... I think, these labels are best avoided," he said.