UK authorities are asserting that they are not pressing panic buttons, at least not yet, in the matter of employing overseas doctors or taking in students from countries under the scanner for terrorist networks.
All eight people arrested in the aftermath of two bungled car bombings here last week are from the medical profession, a British police official said Tuesday, rattling a national heath service that has long relied on foreign doctors to fill its understaffed hospitals.
The seven men are physicians, according to the official, who spoke on condition of anonymity, while the lone woman, the wife of one, is a laboratory technician. The police are now working to unravel links and prior contacts within this far-flung expatriate medical circle.
For the British public, the prospect of highly educated professionals as terror suspects is a chilling departure from the home-grown Muslim terrorists, many with family roots in Pakistan, who have been implicated in previous conspiracies here.
Britain remained jittery on Tuesday, with the police evacuating parts of London's Heathrow Airport after a security scare, stranding hundreds of passengers in a rainstorm. They also carried out "controlled explosions" near a subway station here and outside a mosque in Glasgow.
Meantime fresh details emerged about the men linked to the plot to detonate two car-bombs in London's West End, and an attack the following day at the Glasgow airport, in which two men rammed a Jeep Cherokee into the terminal and set it ablaze.
The driver of the vehicle was another doctor, named Khalid Ahmed, according to an official with knowledge of the investigation. Footage of Dr. Ahmed after the incident, shown on British television on Tuesday, appeared to show a young man. He was severely burned in the fire, and is under guard in a hospital near Glasgow.
On Tuesday, Britain's BBC-2 broadcast an interview with Shiraz Maher, a former member of the Hizb ut-Tahrir, a radical Islamic group, who described himself as a onetime friend of Bilal Abdullah, an Iraqi doctor who was in the Jeep with Dr. Ahmed and is also under arrest.
Mr. Maher said he had known Dr. Abdullah when both men were students in Cambridge, two years ago and believed the man he knew then was the same person in the airport attack.
There was no immediate corroboration of his association with Dr. Abdullah. But Mr. Maher described him as strongly opposed to the occupation of Iraq and to the rise of Shiite power in Iraq.
Doctors and law-enforcement officials struggled to explain what might have drawn these men into violence.
"There's no explanation at this stage why they're doctors, other than that it's a perfect cover," a police official said, on condition of anonymity. "It seems at odds with their profession, which is to look after people."
Abhay Chopada, a colorectal surgeon who emigrated from India in 1994, said that the suspects should be thought of "not as doctors, but as terrorists." Perhaps they had been radicalized by the Iraq war and brought their grievances with them to Britain, he said.
Prasad Rao, chairman of the British International Doctors' Association, called the apparent link to terrorism "beyond belief."
"Even if I were to come across my enemy, my duty is to heal the sick," he said. "How could I remotely plan to kill and maim innocent people? I have no words to describe this."
However, Sandy Bell, the director of homeland security at the Royal United Services Institute, a private policy research body, said that she found it plausible that doctors could become terrorists.
"In the end, these people are attracted to the U.K., to the medical profession, because they are dedicated and bright," she said in an interview. "That not only makes them attractive to any profession, but also to terrorist organizations. It doesn't surprise me that they have been targeted."
On its part the Department of Health bravely insisted vetting was the business of the employers, namely the hospitals offering short-term contracts to overseas doctors. The employers said the checks already in place are extensive.
The vetting, at the moment, focuses on medical qualifications, identity and the applicant's criminal record. There is little scope for picking up radicalisation, militancy or revolutionary tendencies.
The NHS Employers said in a statement that hospital management teams "carry out rigorous checks before they appoint any member of staff, including verification of identity, qualifications, registration and eligibility to work in the UK. The nature of their work means that staff are dealing with people who are vulnerable and we need to be confident that patients are safe".
But there was clear unease at the idea of singling out the overseas doctors for new scrutiny. There are more than 80,000 in Britain.
"While doing all they can to prevent unsuitable people taking up employment in the NHS, employers also have a duty to look after the rights of their staff and this includes not discriminating against employees in any way on the grounds of their religion or belief," said the statement.
Britain's National Health Service has long relied on skilled foreign doctors to meet staffing shortfalls, and foreigners have long been drawn to its relatively generous salaries and exacting standards of training.
While foreign doctors have always had to pass a battery of tests to prove their qualifications and fitness to practice, the rules were tightened last year. Now, most foreign doctors are required to obtain work permits for specific jobs, reducing their chances of finding work.
At least two of the suspects in this case — Dr. Abdullah and Mohammed Asha, a Saudi-born Palestinian — are believed to have come to Britain before this new law took effect.
Overseas doctors can also apply, in competition with doctors in the UK and Europe, for places under the Highly Skilled Migrant Program.
Criminal record checks are mandatory. "It is good practice for an employer to carry out a CRB check even if an applicant claims never to have lived in the UK and a police check in that person's country of origin," said NHS Employers. "We would expect an employer to ask a doctor who is being appointed from overseas to bring their own evidence of police clearance in their home country."
NHS Employers would only advise that hospital trusts should repeat their criminal bureau checks on all junior doctors every three years.