The White House has said fresh allegations of abuse of prisoners in Iraq and Guantanamo Bay by US military personnel will be "fully investigated".
A White House spokesman promised those responsible would be held to account and measures taken to avoid a repeat.
Memos between FBI officials detailing abuses, some dated after the Abu Ghraib jail scandal, were released as part of a legal case against the government.
The case is being brought by the American Civil Liberties Union (ACLU).
Scott McClellan, official spokesman for US President George W Bush, said: "The president expects that if there are allegations of abuse, that those allegations need to be taken seriously.
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"They need to be fully investigated. People need to be held accountable and brought to justice if they're involved in wrongdoing, and preventative measures and corrective measures put in place to prevent it happening again."
He said other allegations that Pentagon interrogators at Guantanamo pretended to be FBI agents to avoid possible blame were a matter for Defence Secretary Donald Rumsfeld.
ACLU executive director Anthony Romero said the documents raised grave questions about who was to blame for widespread detainee abuse.
Last week documents released for the case threw up fresh revelations of abuse in Iraq by US marines, 13 of whom have been convicted and some jailed.
'Executive order'
The documents, obtained through the Freedom of Information Act, are mostly made up of communications between FBI agents concerned at seeing interrogation techniques they are prohibited from using themselves.
One of the memos released on Monday provided the account of an agent who observed "serious physical abuses" in Iraq.
" The detainee was almost unconscious on the floor with a pile of hair next to him - he had been pulling his own hair out throughout the night "
It described strangulation, beatings and the placing of lit cigarettes into detainees' ears.
Another document said an executive order signed by President George W Bush had authorised techniques such as "sleep management", stress positions, use of military dogs and sensory deprivation.
The White House was quick to respond to this allegation, saying: "What the FBI agent wrote in the e-mail is wrong. There is no executive order on interrogation techniques."
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A document relating to Guantanamo suggests that detainees were shackled to the floor in foetal positions for more than 24 hours at a time, left without food and water and allowed to defecate on themselves.
Other allegations contained in the e-mails include:
The department has also said in relation to previous cases that it did not tolerate abusive tactics.
Some allegations in the documents are under investigation, the Pentagon added.
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