Federal inmates throughout the country can go to their prison libraries and hear recorded sermons of the radical American-born Muslim cleric deemed so dangerous that President Barack Obama has authorized killing him. That's the finding of an FBI report issued among law enforcement officials Friday.

Anwar al-Awlaki is believed to be in Yemen and is considered to have inspired a number of attempted and successful terrorist attacks over the years, most recently including the Fort Hood shooting massacre, the failed Christmas Day airline bombing attempt and the failed Times Square car bombing earlier this month.

According to a law enforcement source who has seen the report, Bureau of Prisons (BOP) officials found Awlaki tapes in penitentiaries run by the BOP.

It isn't clear how long those tapes have been on the library shelves. The report did not indicate what action would be taken now that this discovery has been made.

The report seems to validate long-term concerns that prisons and their libraries have served as incubators of radical Islamic activity, and released inmates who have gone on to plot attacks in the United States.