One of the suspects in the 21 July failed attacks in London, Muktar Said Ibrahim, spent time in jail, but did the experience turn him towards radical Islam?
Muktar Said Ibrahim received a five-year sentence for robbery in 1996.
Muktar Said Ibrahim is thought to have become radical in prison
He spent two-and-a-half years at Huntercombe Young Offenders' Institution and Woodhill Prison. It has been suggested he became radicalised while he was in jail.
The Home Office employs 23 full-time and 12 part-time imams to serve over 4,000 Muslim prisoners in the UK. Islam is now the second biggest religious group in British jails.
Richard Reid, who tried to blow up a plane with a "shoebomb", converted to Islam while in Feltham Young Offenders' Institution.
And two prison imams were suspended after 11 September 2001 for making "inappropriate" remarks about the US.
But imams, academics and the government strongly refute the suggestion that imams could be partly to blame for any radicalisation.
Asim Hafiz, imam of Wandsworth prison, said imams are not extreme and they oppose any kind of violence.
"All of the imams that I have spoken to after 7 July have condemned the attacks and that is what they are preaching in prison," he told BBC Radio 4's Today programme.
Professor Dawud Noibi, also an imam who visits Muslim prisoners, said radicalising inmates was "the last thing an imam would do".
"Imams are there not only to look after the welfare and religious needs of Muslim prisoners, but also to help them to rehabilitate."
It is a view shared by criminology professor David Wilson, who has studied the work of Muslim religious leaders in the prison system.
He said there was "no evidence" to suggest they play any part in the radicalisation of prisoners.
"I conducted research with a cross-section of imams who work in prisons and none of them were extremists or jihadists - they were in fact very moderate," he said on BBC One's Breakfast.
Home Office minister Hazel Blears said imams employed by the government were actively combating extremism.
"Not only are they preaching the true Islam, but they are also challenging these ideas with the prisoners," she said.
Message of peace
Imams and experts believe the broader environment of the prisoner could be responsible for radicalisation.
'Shoebomber' Richard Reid converted to Islam at Feltham
Sheikh Hafiz said sometimes prisoners are radicalised before they are put in jail, but he admitted it is possible they meet other prisoners with extreme views.
"What individuals are doing themselves - on the landings, on the wings, in their cells - the prison services and the imams do not have control over that."
He said it was his job to challenge any extremist views held by Muslim inmates.
"I just have to make sure that I stress the true Islamic message - that message is of peace, not of killing, not of chaos.
"The best I can do for those who are vulnerable is to make my services available to them and address these issues openly and frankly."