Nine Pakistani students arrested during anti-terror raids released without charge

Police and counter-terrorism officials were left embarrassed last night after nine Pakistani students suspected of involvement in what Gordon Brown claimed was a "very big plot" against the UK were released without charge.

The nine were due to be deported after being handed over to the UK Border Agency. Two remaining suspects are still being questioned by Greater Manchester police. The move came after investigators spent 13 days searching for evidence following the arrests from a number of addresses in Greater Manchester, Liverpool and Lancashire under the Terrorism Act.

The raids led to the resignation of the country's leading counter-terrorism officer, Bob Quick, after he inadvertently allowed details of the operation to be photographed. Before the men had been interviewed the prime minister spoke of how the police had foiled a "very big plot", but as early as last Monday it emerged the government had spoken to Pakistani officials seeking reassurances that if the men were deported they would not be tortured.

The Guardian understands the decision to arrest the suspects on 8 April came after a three-way row between MI5, senior officers in the Metropolitan police and the Greater Manchester police. MI5 were strongly of the opinion that the arrests should wait while more intelligence was gathered. But in an example of the tensions between Whitehall counter-terrorism officials and their counterparts in the police, the decision was made to take "executive action" even though the intelligence suggested there was little evidence to charge the suspects.

It is understood anti-terrorist officers in the Met disagreed with their counterparts in Greater Manchester that the arrests should be made. But the concern that there was a threat to the public led to the decision being made to move in.

Investigators had desperately hoped they would find something at the suspects' homes. But after initially hunting for, and failing to find bomb-making equipment, they turned to the computers with their fingers crossed that some evidence of a plot would turn up. They found nothing substantial.

Despite media reports and the plot being talked up by Brown, there was never any evidence that the suspects had identified targets for an attack.

The arrests came several hours earlier than the police had planned after Quick accidentally allowed a top secret briefing document on the raids, Operation Pathway, to be caught on camera by a photographer outside Downing Street when he went to brief ministers on the action. The error led to his resignation after politicians condemned the security breach.

But although police sources said bringing forward the arrests may have compromised the operation, it was only brought forward by hours, which is unlikely to have substantially reduced the amount of evidence available to investigators.

Greater Manchester police said last night that the nine men, aged between 22 and 38, had been transferred into the custody of the UK Borders Agency. The Home Office said: "We are seeking to remove these individuals on grounds of national security. The government's highest priority is to protect public safety. Where a foreign national poses a threat to this country we will seek to exclude or to deport, where this is appropriate."

Officers from the north-west counter -terrorism unit arrested the 12 men under the Terrorism Act following the raids on 8 April. Of the 12 men initially arrested, 11 are Pakistani nationals, 10 held student visas and one is British.

Greater Manchester police said searches were continuing at a property in Cheetham Hill, Manchester. "Protecting the public is the main focus of the police. These arrests were carried out after a number of UK agencies gathered information that indicated a potential risk to public safety," the force said. The 12th suspect, an 18-year-old, was released without charge and handed to the Border Agency for deportation on 11 April.

The arrests led to claims that the student visa system contained loopholes which allowed abuse by people attempting to enter the country for illegal activities.

The government has admitted that the system is flawed and, two weeks ago, introduced tougher measures designed to root out false applications. At the time of the arrests counter-terrorism sources expressed the fear that al-Qaida was using Pakistani students not known to the security services.