A Scotland Yard special squad is investigating extremists who protested against Muslim cartoons over the last week.
The investigation began as it emerged that a man who dressed as a suicide bomber during the protests had served a prison sentence for drug dealing.
Omar Khayam, 22, was sentenced to six years in prison in 2002 for possessing crack cocaine with intent to supply, according to newspaper reports.
Although he was released on parole last year after serving half his sentence, he is still on licence and could now be recalled back to jail if he has breached his conditions.
On Monday Mr Khayam, from Bedford, apologised "wholeheartedly" for his behaviour in the London protests, saying it was "wrong, unjustified and insensitive" to dress as a suicide bomber.
The student had been pictured outside Denmark's embassy wearing a simulated suicide bombing outfit to denounce the cartoons first pictured in a Danish paper satirising the Prophet Muhammad.
Officers from the Metropolitan Police travelled to Bedfordshire on Monday with the intention of speaking to Mr Khayam about the incident but returned without interviewing him.
This has now sparked speculation that he may be in trouble with the authorities for breaching his terms of licence.
Downing Street condemned the demonstrations as "completely unacceptable" and Scotland Yard announced a special squad had been set up to investigate the placard-wielding extremists.
No 10 and ministers, including Home Secretary Charles Clarke, queued up to pledge full support for any police action against those who caused outrage by promising death to Europeans after publication of the cartoons.
