Four British prisoners freed from the U.S. military base in Guantanamo Bay, Cuba, have returned to London -- and were immediately arrested by British police.
Police arrested them under Britain's anti-terrorism laws. Prosecutors will decide if there is enough evidence to put them on trial.
A fifth freed British prisoner was held for questioning by immigration officials at a British air base.
The five left Guantanamo Tuesday after Britain promised the Pentagon it will ensure they no longer pose a security risk. They had been at Guantanamo for more than two years.
U.S. Defense Secretary Donald Rumsfeld said Tuesday their release to Britain was appropriate, but called their two-year detention "a good thing."
About 650 prisoners are being held at Guantanamo as "enemy combatants" because of suspected ties to al-Qaida or the Taleban. Most of them were arrested in Afghanistan.
Four other Britons remain at the U.S. base. Senior U.S. officials told a British newspaper earlier this week they believe the four are al-Qaida trained assassins and bomb-makers.
At least one faces a U.S. military trial that could result in the death penalty. Britain is urging U-S officials to allow the British detainees to have access to lawyers and the right of appeal.
The United States has so far freed 88 suspects from Guantanamo -- including Russians, Afghans, and Pakistanis -- and transferred 12 others elsewhere for continued detention.