Radical Muslim cleric Anwar al-Awlaki had been taken into custody by US authorities but released, a conservative human rights watchdog has revealed.
AFP reported Judicial Watch discovered through a Freedom of Information request that the radical cleric, who was killed in Yemen last year in a drone attack, had been held by the US at least twice.
Prior to his death, he had been tied to 26 terrorism cases and was described by the United States as head of the terror network's most effective and lethal franchise.
The documents uncovered indicated he had been held for at least eight months between late 2006 and mid 2007.
In August, Fox News reported the FBI admitted publicly that when the radical Muslim cleric returned to the US in October 2002 he was detained and then abruptly released from federal custody.
President Barack Obama authorized the cleric's targeted killing in 2010 after the CIA concluded he was involved in anti-US plots, the London Telegraph reported.
The targeting was rare and unprecedented for an American citizen.