LONDON — LONDON -- With eight suspects in two failed car bombings in police custody, Britain lowered its national threat level to severe yesterday, while announcing that it would review its procedures for screening foreign-born doctors.
Britain's home secretary, Jacqui Smith, said the decision to lower the threat from critical - its highest level - had been made after authorities concluded there was "no intelligence to suggest that an attack is expected imminently."
But, she said, "there remains a serious and real threat against the United Kingdom, and I would ask that the public remain vigilant."
Days after the bungled attempts to blow up vehicles in London and at Glasgow's airport, the police are confident that the main suspects have been rounded up, a police official said, speaking on condition of anonymity.
Attention is now turning to unraveling the links within this multinational circle of seven doctors and one of their wives to determine how their network was organized. Investigators swarmed over two houses in Liverpool, where one of the arrested doctors was believed to have lived.
Police officers carried out bags stuffed with computer hard drives and documents from the two-story brick rowhouses.
Already, the web extends to Bangalore, India, where two suspects went to the same medical school, and Brisbane, Australia, where one of them was picked up by police while trying to board a flight.
"There are various overseas connections," the official said. "It's possible there may be an interesting Iraqi angle."
The possibility of links to al-Qaida leaders in Iraq was underscored by an Anglican cleric living in Iraq who said he was warned in April about attacks in Britain.
The cleric, Canon Andrew White, said that at a gathering of Iraqi religious leaders in Amman, Jordan, on April 18, one of them said mysteriously that "those who cure you will kill you."
At the time, he did not pay much attention, White said in a telephone interview, and he did not mention it to British officials when he told them about the meeting. However, when he saw that doctors were suspects in the car bombs in London and the attack on the Glasgow airport, he recalled the warning, he said.
"I was told afterward," White said, "that he was closely connected to al-Qaida, but I don't know definitely that he was connected to al-Qaida."
He declined to identify the man by name but said he was a religious leader from Anbar province, a Sunni Arab area of Iraq.
Investigators are re-examining evidence from a 2004 case in which a British convert to Islam plotted to use limousines packed with gas canisters to blow up buildings. The man, Dhiren Barot, was described in prosecution testimony as a senior al-Qaida operative who had attended terrorist training camps in Pakistan and possibly Afghanistan, and had drawn up plans for coordinated attacks in the United States and Britain.
In November he was sentenced to 40 years, later reduced to 30 years because he had not tried to carry out the attacks. Seven accomplices were sentenced to jail terms of 15 to 26 years.
While the lowering of the threat level might soothe nerves here, people are shaken by the disclosure that the suspects worked under the umbrella of Britain's National Health Service.
Britain will conduct a thorough review of its policies for screening foreign doctors who want to practice here, Prime Minister Gordon Brown announced yesterday. Speaking in Parliament, he said the government would also expand its worldwide "watch list."