NEW YORK — It's Friday on Rikers Island, time for weekly worship for nearly a quarter of the city jail's 14,000 inmates.

The men, Muslims, file quietly into a classroom of white cinderblock that serves as their mosque and sit on sheets stamped "Department of Corrections" covering the linoleum floor. Imam Menelik Muhammad stands before a wall facing Mecca and preaches.

"You will not be considered a Muslim unless people are considered safe from your hands and your tongue," he tells the prisoners.

Across the United States, tens of thousands of Muslims are practicing their faith behind bars. Islam is most likely to win American converts there, according to U.S. Muslim leaders, and the religion has for decades been a regular part of prison culture.

But the Sept. 11, 2001, attacks have brought new scrutiny to Muslim inmates, many of whom are black Americans. While prison chaplains of various faiths argue that Islam offers a path to rehabilitation, others say it has the potential to turn felons into terrorists.

FBI director Robert Mueller told the Senate Intelligence Committee in February that "prisons continue to be fertile ground for extremists who exploit both a prisoner's conversion to Islam while still in prison, as well as their socio-economic status and placement in the community upon their release."

The reality is harder to read: Those on opposing sides have such divergent views they seem irreconcilable. Who's right matters not only for national security, but also for the development of American Islam itself as it struggles for acceptance alongside the major U.S. faiths.

Ever since the 2002 arrest of Jose Padilla, an American Muslim convert who authorities say planned a "dirty bomb" radiological attack after he left jail, politicians, law enforcement officials and even a few evangelical leaders have warned that Muslim inmates are ripe for terrorist recruitment.

Chuck Colson, founder of Prison Fellowship Ministries and a Nixon administration official, predicted that "radical Islamists will use prisons" to avenge Islam.

Prison chaplains and others, however, say such warnings are dangerously ignorant.

In interviews with The Associated Press, chaplains, prison volunteers, correctional officials, inmates and former inmates all insisted that there was no evidence of terrorist recruitment by Muslims in their prisons — although banned pamphlets and books sometimes slip in.