Attorney General Eric H Holder Jr said that a two-year review by a specially appointed prosecutor, John H Durham, had determined that any further investigation into that large group of cases “is not warranted.” The inquiry into the two deaths, though, could result in criminal charges against Central Intelligence Agency officers or contractors.

Intelligence officials saw the announcement as a vindication of sorts.

“I welcome the news that the broader inquiries are behind us,” Leon E Panetta, director of the CIA, said in his last day in office before being sworn in Friday as defense secretary. “We are now finally about to close this chapter of our agency's history.”

Still, the renewed attention to the volatile issue of CIA interrogations — after the controversy had all but disappeared from public debate — is sure to set off a range of legal and political challenges for the Justice Department, the White House and lawmakers on both sides of the aisle.

The Justice Department has faced years of criticism from the left for inaction on accusations of abuse by CIA interrogators, while defenders of the CIA have warned that any prosecutions would be deeply damaging to the agency. It will be left to Gen. David H Petraeus, who was confirmed Thursday as CIA director, to lead the agency through any turmoil from the criminal investigation.

The Justice Department did not identify the two detainees at the center of the criminal investigation. But government officials, who spoke on condition of anonymity because of the continuing review, said the first case involved the well-publicized death of Manadel al-Jamadi, who died in CIA custody in 2003 at Abu Ghraib prison in Iraq. He became publicly known as the Iceman after his body was photographed packed in ice and wrapped in plastic.

The second case involves the death of Gul Rahman, suspected of being a militant, who died in 2002 after being shackled to a concrete wall in a secret CIA prison in Afghanistan known as the Salt Pit, the officials said.

Beginning in 2002, Justice Department lawyers wrote a series of then-secret legal opinions authorizing intelligence officers to use increasingly harsh interrogation methods like sleep deprivation, slapping and waterboarding on dozens of terrorism suspects in an effort to elicit information about Al Qaeda.

Mr. Holder stressed Thursday in his statement, as he has before, that any intelligence officials who acted “in good faith” within the scope of the Justice Department's legal guidance at the time would not face prosecution. The review that led to the full criminal investigations focused primarily on whether “unauthorized interrogation techniques were used by CIA interrogators” and, if so, whether they amounted to criminal violations of statutes against torture or other measures, he said.

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In a nod to the tensions surrounding the issue, Mr. Holder was careful to emphasize the “incredibly important service to our nation” that intelligence officials provide. “They deserve our respect and gratitude for the work that they do,” he said.

Civil rights leaders said Thursday that they were disappointed that Mr. Holder had not set a broader target for the current investigation by looking at the legality of the interrogation policies approved by senior lawyers and intelligence officials.

“With the approval of the Bush administration's most senior officials, the CIA operated an interrogation program that subjected prisoners to unimaginable cruelty and violated both international and domestic law,” said Jameel Jaffer, deputy legal director for the American Civil Liberties Union. “The narrow investigation that Attorney General Holder announced today is not proportionate to the scale and scope of the wrongdoing.”

But Representative Mike Rogers, a Michigan Republican who leads the House Intelligence Committee, said the Justice Department's decision to close the book on all but two of the remaining cases “has finally substantially lifted an undeserved cloud of doubt and suspicion from all of our intelligence professionals.”

President Obama signaled soon after his inauguration in January 2009 that he was reluctant to re-examine some of the most controversial counterterrorism tactics of the George W. Bush administration, including the treatment of prisoners and the use of harsh interrogation tactics.

Before Mr. Obama took office, though, Attorney General Michael B Mukasey appointed Mr. Durham, a longtime organized-crime prosecutor from Connecticut, to examine evidence that the CIA had improperly destroyed videotapes of interrogations in possible violation of court orders. The Justice Department declined to bring charges over the tapes' destruction, but Mr. Holder, in 2009, expanded Mr. Durham's inquiries to include possible mistreatment of prisoners.

Justice Department prosecutors and other officials, including the CIA inspector general's office, began examining the tactics of American captors as early as 2004 to determine whether the use of the tough interrogation tactics may have violated laws or government policies.

Federal prosecutors in Alexandria, Virginia, looked into cases involving more than two dozen detainees, including Mr. Ramadi and Mr. Rahman. The Justice Department has not brought any charges to date.

Law enforcement and intelligence officials declined to discuss in detail the nearly 100 cases involving detainee treatment that have been dropped. It is not clear if any involved deaths.

Among those cases, an American official said Thursday, was one in which a CIA interrogator told Abd al-Rahim al-Nashiri, charged with plotting the 2000 bombing of the Navy destroyer Cole, that failure to cooperate could result in his family members' being brought to prison. According to a 2004 report by the CIA inspector general, the interrogator wanted Mr. Nashiri to infer for “psychological” reasons that his female relatives might be sexually abused.

The Justice Department's review of the CIA cases angered Mr. Mukasey, Mr. Holder's predecessor. In an interview last month, Mr. Mukasey said the department's scrutiny of the CIA interrogation cases was “absolutely outrageous” and “an unconscionable thing to do.”

He and other opponents of the continuing investigations said prosecuting CIA officials over the interrogations would not only demoralize the agency, but also unfairly penalize intelligence officials who believed they were acting under clear legal authority to protect the country.

Senator Charles E Grassley, Republican of Iowa and the ranking member of the Judiciary Committee, expressed relief on Thursday at having some resolution.

“Perhaps now our intelligence professionals in the field can stop looking over their shoulders,” he said, “and the attorney general will quit armchair quarterbacking from Washington, DC, intelligence decisions in the field.”