A policeman in Frankfurt airport’s main terminal. (Reuters)

London, Dec. 28: The British government said today that it had acted earlier this year to reject a bid for a renewed student visa from the Nigerian man accused in the failed Detroit airliner bombing plot.

It also said that the suspect was placed on an official watch list to prevent him from re-entering Britain.

In a BBC radio interview, home secretary Alan Johnson also said he did not believe the suspect, Umar Farouk Abdulmutallab, was acting alone in the plot. Investigators say Abdulmutallab tried to set off an explosive package taped to his leg as a Northwest Airlines plane approached Detroit airport with nearly 280 passengers and crew on a flight from Amsterdam on Christmas Day.

Johnson gave no reason for suggesting Abdulmutallab may have had accomplices. But he noted that Scotland Yard and Britain’s security services were investigating whether the alleged would-be bomber was radicalised in his Islamic beliefs while he was a mechanical engineering student from 2005 to 2008 at University College London (UCL), one of Britain’s elite academic institutions.

Johnson said Abdulmutallab’s application to renew his student visa was rejected in May after officials determined that the academic course he had given as his reason for returning to Britain was bogus.

He was then placed on the watch list, Johnson said, a procedure that would normally involve American authorities being informed of the action Britain had taken.

But Johnson was vague about whether authorities in the US had been officially informed of the action, although he said he doubted there had been a “hiccup” in the process.

His vagueness appeared to be part of a wider uncertainty on the part of British authorities as they scramble to learn more about Abdulmutallab’s activities in Britain and his associates while he was studying there.

The rejection of the visa renewal appeared to have been part of a wider process initiated by British authorities earlier this year, when they launched a crackdown against so-called “bogus colleges” officials said were established in large numbers across Britain in a bid to elude tightened immigration controls.

Saying the colleges had been used to obtain thousands of fraudulent student visas, the home office has closed about 2,000 such colleges in the last six months. The prestigious UCL was not part of the crackdown.