Although none of the suspects were charged, a report by Lord Carlile, the independent reviewer of terrorism legislation, said the students could have ties with Al-Qaeda.

Carlile said intelligence suggested that all the arrested Pakistani students may be a part of some “very significant international plot”, details of which are yet to be traced.

According to The Telegraph, probe into the Easter bombing plot led the investigators to one Najibullah Zazi, the alleged mastermind of a plot to attack the New York subway.

It is believed that Zazi, who was arrested in Colorado in September along with other members of his group had purchased huge quantities of some key bomb making materials such as hydrogen peroxide and acetone products.

Carlile, in his report, identified Abid Naseer as the ‘central figure’ in the Easter plot, and is believed to be ‘connected to an Al-Qaeda source situated abroad.’

“There was intelligence to suggest that he might be involved in planning operational activity in the UK and was in direct contact with a significant attack planning group situated outside the UK,” Carlile said.

“Analysis of intelligence material on a wide front suggested strongly to the services concerned that this might well be part of a very significant international plot,” he added.

The report also criticised the British authorities for failing to table evidence against the arrested students.

Carlile said the police had failed to understand the law properly on detaining terror suspects.

“I am surprised that the police did not anticipate that they would be required to clarify the evidential basis for the arrests before a judge during the period of detention,” he said.