Washington ? Prisons are attracting increasing attention from law enforcement as breeding grounds for terror groups seeking malcontents who can use their American citizenship to blend into society and carry out attacks.

The capture of homegrown terror suspect Jose Padilla, who the United States says was plotting for a radioactive “dirty bomb,” is a reminder that the nation could have potent enemies within.

Imam Rafiq Mahdi, left, a religious leader at the Masjid Al-Iman mosque in Fort Lauderdale, Fla., and Broward County Sheriff Ken Jenne, speak about religious opportunities available to inmates in Broward County prisons. Under federal law, prisons must allow inmates access to religious leaders and texts but they don't have to allow religious groups that advocate violence to minister.

“Our prisons are stuffed full of people who have a hatred of the prison administration, a hatred of America and have nothing but time to seethe about it,” said Robert Fosen, former assistant commissioner of New York state prisons.

“Oftentimes they want a way to lash out or feel important. They are very likely to join groups that facilitate that anger. Anti-American feelings help all sorts of gangs recruit in prison.”

Padilla, 31, a New York City native and former Chicago gang member who also goes by Abdullah al Muhajir, is the first American accused of bringing al-Qaida’s terrorist campaign to U.S. soil.

In 1992, Padilla was sent to a Florida jail for pulling a gun on another driver. When arrested, he identified himself as Catholic, according to police. U.S. officials believe Padilla converted to Islam while in jail and headed to Afghanistan and Pakistan in the late 1990s.

Being in prison not only contributes to hard feelings, it can sometimes provide a harbor for terrorists to act against the United States within its own borders.

Sheik Omar Abdel-Rahman, serving a life sentence in New York for plotting to blow up landmarks, is accused of sending messages from prison through visiting attorneys that directed terrorist acts to followers.

Officials at the U.S. Marshals Service, responsible for guarding accused American Taliban John Walker Lindh and Zacarias Moussaoui, accused of conspiracy in the Sept. 11 attacks, say they are taking extra precautions to make sure no criminal contacts occur.

Prisons and jails are adjusting to the nation’s need to keep track of dissidents.

In New York, a senior prison official said the prisons have asked Islamic religious groups whether they support terrorist groups. The official, speaking on condition of anonymity, said one group has been barred from ministering at the prisons. The official declined to identify the group.

In Florida, prison officials said the Sept. 11 terrorist attacks have not led to new policies security was already high but they raised awareness that some religious groups could be linked to illegal activities.

“We examine and look at every group, religious included, as a possible threat to security of the institution, to the staff and to inmates,” said Sterling Ivy, spokesman for the Florida prison system. “We are constantly analyzing all aspects of religion in prison, but at the same time we must maintain a sense of religious freedom based on the Constitution.”

Alex Taylor, chief chaplain for Florida prisons said, “After Sept. 11, a lot of prisoners tried to tell us that this is what the Muslim prison groups were preaching. It was looked into and there were no sustainable accusations.”

Authorities have also been monitoring contacts between American extremists and foreign terrorist groups to make sure they don’t collaborate on attacks. These include neo-Nazis, white supremacists and Black Muslim factions.

All three of those groups have a history of recruiting in prison. In the 1980s, several groups of skinheads used prisons in Los Angeles as a recruiting ground. In the 1960s, the Black Panthers reached out to prisoners, offering legal advice and membership.

Under federal law, prisons must allow inmates access to religious leaders and texts. But they don’t have to allow religious groups that advocate violence to minister.