The Army general who investigated the abuses at Abu Ghraib prison outside Baghdad said yesterday that he had found no evidence the misconduct was based on orders from high-ranking officers or involved a deliberate policy to stretch legal limits on extracting information from detainees.

Instead, Maj. Gen. Antonio M. Taguba attributed the scandal to the willful actions of a small group of soldiers and to "a failure of leadership" and supervision by brigade and lower-level commanders.

Similarly, the Army's top intelligence officer, Lt. Gen. Keith B. Alexander, sought to portray the abuse as the deeds of a handful of military police soldiers, with the peripheral involvement of U.S. military intelligence personnel in Iraq.

But several senators challenged the notion that low-ranking soldiers could have devised the particularly humiliating measures on their own, and Taguba reported that military guards probably were influenced by intelligence personnel. He also clashed openly with the Pentagon official responsible for intelligence, Stephen A. Cambone, over the propriety and significance of a decision last November to place Abu Ghraib prison under the command of a military intelligence officer.

Appearing before a Senate panel investigating the prison scandal, Taguba testified that the move made military guards subject to the tactical control of interrogators, thus violating Army doctrine and blurring lines of responsibility. Cambone defended the decision as consistent with military standards and helpful to improving the gathering of intelligence.

Revealing the interrogation methods allowed in Iraq, the Armed Services Committee released a single-page titled "Interrogation Rules of Engagement," listing two categories of measures. The first showed basic techniques approved for all detainees, while the second involved tougher measures that required approval by Lt. Gen. Ricardo S. Sanchez, commander of U.S. forces in Iraq. Among the items on the second list were stress positions for as long as 45 minutes, sleep deprivation for as long as 72 hours and use of muzzled dogs.

Cambone said the Bush administration's policy has been to apply the Geneva Conventions to the interrogation and other treatment of detainees in Iraq. But several senators expressed doubts about whether some of the listed techniques conform with international limits.

Yesterday's hearing marked the first public appearance by Taguba since results of his investigation, along with photographs documenting abuse, burst into public view over the past two weeks. The disclosures have set off an international furor, undercutting U.S. efforts to stabilize Iraq and prompting calls by Democratic lawmakers and some newspapers for Defense Secretary Donald H. Rumsfeld to resign.

Rumsfeld has said he will not step down to appease political critics but will leave if he deems he can no longer be effective. He picked up support yesterday from a Republican senator who had been withholding judgment.

"I think it would be unfair for him to take a fall if this is just a limited activity of a few people or of a prison poorly run," Sen. Lindsey O. Graham (S.C.) said.

Democrats voiced frustration at conflicting accounts from military and civilian officials, but for the most part, senators muted their differences and focused on trying to resolve one of the core questions of the scandal -- namely, whether the abuses were essentially the result of a few errant soldiers and private contractors, or reflected a misguided command structure and interrogation policies that neglected human rights.

Taguba, 53, a Philippine-born two-star general with a reputation as a straight shooter, drew praise from members of both parties for a thorough and objective inquiry into the mistreatment. Asked by Sen. John W. Warner (R-Va.), the committee chairman, to put "in simple words" how the abuses happened, Taguba said: "Failure in leadership, sir, from the brigade commander on down. Lack of discipline, no training whatsoever and no supervision. Supervisory omission was rampant."

Pressed by several senators on whether any order had been given to the guards "to soften up" the detainees prior to interrogation, Taguba said he discovered none, nor any "overall military or intelligence policy" to do so. But he said that the military guards who have been charged with committing the abuses were influenced by military intelligence personnel and private contractors responsible for interrogations.

"We did not find any evidence of a policy or a direct order given to these soldiers to conduct what they did. I believe that they did it on their own volition," said Taguba, who was deputy commander for military support operations in the Persian Gulf region when he led the investigation.

Taguba's 6,000-page report laid much of the leadership blame on Brig. Gen. Janis L. Karpinski, commander of the 800th Military Police Brigade, and Col. Thomas M. Pappas, commander of the 205th Military Intelligence Brigade, as well as on several subordinates.

Karpinski has received a letter of admonishment in connection with the abuse. She has not been charged, but seven military police soldiers under her command face courts-martial. Seven other officers and sergeants have been reprimanded. An investigation is underway into the role of military intelligence.

Taguba testified that friction arose between Karpinski and Pappas when Pappas was put in charge of Abu Ghraib last November. Taguba said the move, ordered by Sanchez, violated Army doctrine by making military police subordinate to interrogators.

Cambone defended the decision, saying it was intended to improve prison management and did not mean military police operations came under the control of military intelligence officers.

The dispute drew expressions of frustration from some senators.

"When we were talking about the abuses that are taking place with the military police and you have two entirely different kinds of viewpoints on this issue, how in the world are the military police that are supposed to implement going to be able to get it straight?" asked Sen. Edward M. Kennedy (D-Mass.).

A further disagreement arose between Taguba and Cambone over the impact of a visit to Iraq last August by Maj. Gen. Geoffrey D. Miller, then commander of the detention facility at Guantanamo Bay, Cuba, which holds terrorist suspects.

Cambone said he had encouraged the visit to enable Miller to advise on improving interrogation techniques in Iraq and speeding the flow through official channels of information gleaned. One of Miller's recommendations was that military police should facilitate the work of military interrogators.

Taguba said Army rules prohibit involving military police in setting conditions for interrogations. Cambone said Miller did not propose "setting conditions" but rather a more "cooperative attitude" between the guards and interrogators, which he said was appropriate.

Appearing with Cambone and Taguba, Lt. Gen. Lance Smith, the deputy commander of U.S. Central Command, testified that Miller had given brigade commanders in Iraq a list of the coercive measures used in interrogations at Guantanamo Bay.

But Smith added that Miller had made clear to the commanders that "many" of the measures could not be used in Iraq because of the Geneva Conventions. Miller took over last month as commander of all detention facilities in Iraq.

Despite such testimony, several Democratic senators, including Jack Reed (R.I.) and Hillary Rodham Clinton (N.Y.), voiced continued suspicions that a connection exists between Miller's trip and the spate of alleged abuses that occurred shortly afterward, between October and December.

Questioned about what he and other senior Pentagon officials knew of complaints by the International Committee of the Red Cross about prison conditions in Iraq, Cambone said Red Cross reports last fall did not reach the Pentagon but went directly to U.S. commanders in Iraq. He said he knew of concerns last year by L. Paul Bremer, the top U.S. administrator in Iraq, but said those had involved a desire to see faster processing and release of detainees. Bremer did not begin to voice concerns about specific conditions in the prisons until February, when the Red Cross submitted a summary report, Cambone said.

At a second hearing yesterday afternoon, Alexander, the Army's top intelligence officer, repeatedly sought to distance military intelligence from what he described as the reprehensible actions of a few poorly led military police soldiers. But several senators from both parties expressed skepticism.

"There's all kinds of evidence that military intelligence is involved here," Sen. Carl M. Levin (D-Mich.) said.

After the hearings, Warner announced on the Senate floor that an agreement had been reached with the Pentagon to allow senators access to those photographs and computerized video not yet made public. Warner said senators could view the photos today in a secure room in the Capitol. The photos will remain in Pentagon custody, he said.

"Supervisory omission was rampant," Maj. Gen. Antonio M. Taguba told a Senate committee.