British officials on Wednesday eased the security alert from critical to severe because police believe they have rounded up the main suspects linked with three failed car bombings in London and Glasgow.

Authorities raised the security alert to critical — meaning an attack is imminent — after discovering two explosives-packed cars in London on Friday. A day later, a fuel-laden jeep rammed into Scotland's Glasgow airport and burst into flames.

When the level is at "severe," further attacks are considered likely. Britain's alert level has been at the severe stage since last August.

Home Secretary Jacqui Smith said in a statement that the reduction does not mean the overall threat has gone away.

Police have arrested eight suspects since the failed attacks, a group authorities believe are the key members of the alleged ring, said reports. However, there are unconfirmed reports police are searching for at least one more British-born suspect.

The eight people held include one doctor each from Iraq and Lebanon, along with two from India. There is also a Jordanian doctor and his medical assistant wife. Another doctor and a medical student are thought to be from the Middle East.

Six of the suspects are being questioned in London. One suspect is being held in Australia, where he was arrested and the eighth remains in a Scottish hospital critically ill with burns.

None of the suspects has been charged. Under British laws, suspects can be held for 28 days before charges must be laid, with the possibility of another 90-day extension.

Little is known about the suspects, who were employees of Britain's National Health Service and worked at hospitals in England and Scotland.

The names of some of the suspects were already on a British intelligence agency database, which helped police round up the suspects so quickly, say British news reports.

The Times of London reported Wednesday that an al-Qaeda leader in Baghdad warned a British Anglican minister last week of an imminent attack on British targets.

Canon Andrew White, who works in Iraq, told the Times that an unidentified al-Qaeda leader warned him that his group was planning an attack and that "those who cure you will kill you."

With files from the Associated Press