'Leaked confidential documents have revealed that senior officials from the former US administration had warned a 9/11 investigation panel against probing too deeply into the terrorist attacks.

In a letter obtained by the American Civil Liberties Union (ACLU), the 9/11 Commission was refused permission to question terror suspects, with the Bush administration arguing that by doing so the panel would "cross" a "line" and obstruct the administration's efforts to protect the nation.

Citing the need to "Safeguard the national security, including protection of Americans from future terrorist attacks," the government officials demanded the Commission not make further attempts at conducting a deeper probe into the September 11 terror attacks.'

Read more: '9/11 Panel Was Warned Not to Probe Too Deeply'