British police have cleared the youngest of 12 men arrested in connection with what officials call a "very big" terrorist plot.

Police say the 18-year-old was released without charge Saturday and is now being questioned by British immigration officials.

Meanwhile, a court ruling is giving police another week to interrogate the other suspects, most of them Pakistanis in Britain on student visas. 

Police detained the men Wednesday in a series of raids across northwestern England and continue to search 10 sites in Manchester, Liverpool and Lancashire.

British authorities have not released details of the alleged plot but secret documents photographed by the media before the raids show authorities suspect the it was linked to al-Qaida. 

Pakistan's interior minister said Saturday that Pakistan wants to verify the identity of the suspects.

Rehman Malik told reporters Pakistan wants to bring the culprits to justice, especially if they had any ties to al-Qaida.

British Prime Minister Gordon Brown telephoned Pakistani President Asif Ali Zardari this past week to discuss terrorist threats from Pakistan.  Mr. Brown said Thursday that Pakistan needs to do more to handle the threat.

Pakistan's High Commissioner to Britain, Wajid Shamsul Hasan, said Friday that his country is doing all it can to deal with the terrorist threat and that it is Britain that needs to do more.

Britain's Home Office said Friday that all foreign students are closely investigated -- including checking their fingerprints -- before being issued student visas.  The office said those procedures have been tightened recently.

The security lapse forced police to act on their investigation earlier than they had planned and prompted the resignation of Britain's top counter-terrorism officer.

Britain says it has foiled two major bomb attacks since July of 2005, when attacks on London's transit system killed 52 people.  Authorities said all of the plots had links to Pakistan.

Some information for this report provided by AP, Reuters and AFP.