WASHINGTON — Medical personnel were deeply involved in the abusive interrogation of terrorist suspects held overseas by the Central Intelligence Agency, including torture, and their participation was a “gross breach of medical ethics,” a long-secret report by the International Committee of the Red Cross concluded.

Based on statements by 14 prisoners who belonged to Al Qaeda and were moved to Guantánamo Bay, Cuba, in late 2006, Red Cross investigators concluded that medical professionals working for the C.I.A. monitored prisoners undergoing waterboarding, apparently to make sure they did not drown. Medical workers were also present when guards confined prisoners in small boxes, shackled their arms to the ceiling, kept them in frigid cells and slammed them repeatedly into walls, the report said.

Facilitating such practices, which the Red Cross described as torture, was a violation of medical ethics even if the medical workers’ intentions had been to prevent death or permanent injury, the report said. But it found that the medical professionals’ role was primarily to support the interrogators, not to protect the prisoners, and that the professionals had “condoned and participated in ill treatment.”

At times, according to the detainees’ accounts, medical workers “gave instructions to interrogators to continue, to adjust or to stop particular methods.”

The Red Cross report was completed in 2007. It was obtained by Mark Danner, a journalist who has written extensively about torture, and posted Monday night with an article by Mr. Danner on the Web site of The New York Review of Books. Much of its contents were revealed in a March article by Mr. Danner and in a 2008 book, “The Dark Side,” by Jane Mayer of The New Yorker, but the reporting of the Red Cross investigators’ conclusions on medical ethics and other issues are new.

Khalid Shaikh Mohammed, the chief planner of the Sept. 11 attacks, told investigators that when he was waterboarded, his pulse and oxygen level were monitored, and that a medical attendant stopped the procedure on several occasions.

Another prisoner, Walid bin Attash, who had previously had a leg amputated, said that when he was forced for days to stand with his arms shackled above his head, a health worker periodically measured the swelling in his intact leg and eventually ordered that he be allowed to sit.

The report does not indicate whether the medical workers at the C.I.A. sites were physicians, other professionals or both. Other sources have said that psychologists helped design and run the C.I.A. interrogation program, that physicians’ assistants and former military paramedics worked regularly in it, and that physicians were involved at times.

By policy, the Red Cross, the chief independent monitor of detention conditions around the world, keeps its reports to governments confidential to encourage officials to grant access to prisoners. Bernard Barrett, a spokesman for the organization in Washington, declined on Monday to comment on the report, adding, “We deplore that confidential material attributed to the I.C.R.C. was made public.”

Mark Mansfield, a C.I.A. spokesman, said that because of the Red Cross’s confidentiality policy, he would not comment on the report. He said that President Obama had prohibited all government interrogators from using techniques apart from the noncoercive methods in the Army Field Manual, and that the new C.I.A. director, Leon E. Panetta, “has taken decisive steps to ensure that the C.I.A. abides by the president’s executive orders.”

Mr. Mansfield added, however, that Mr. Panetta “has stated repeatedly that no one who took actions based on legal guidance from the Department of Justice at the time should be investigated, let alone punished.” The C.I.A.’s interrogation methods were declared legal by the Justice Department under President George W. Bush.

In its 40-page report, the Red Cross roundly condemned the C.I.A. detention program not only for using torture and other cruel treatment, but also for holding prisoners without notice to governments or families.

“The totality of the circumstances in which the 14 were held effectively amounted to an arbitrary deprivation of liberty and enforced disappearance, in contravention of international law,” said the report, which was provided to the C.I.A. acting general counsel, John Rizzo, in February 2007.

Shortly after taking office in January, Mr. Obama ordered the C.I.A. secret detention program closed and directed that the Red Cross be promptly informed of every person detained by the C.I.A. or any other agency.

The report also provided new details of the Bush administration’s failure to cooperate for several years with the Red Cross’s inquiries and investigations of American detention programs. Repeated inquiries and reports from the organization beginning in 2002 received no response from American officials, the report said, though the United States sent a diplomatic message addressing some inquiries in 2005.

M. Gregg Bloche, a Georgetown University law professor, who also trained as a psychiatrist and is now a visiting professor at the University of Chicago law school, called the report’s findings “a disturbing confirmation of our worst fears about medical professionals’ involvement in directing and modulating cruel treatment and torture.”

Another critic of medical involvement in harsh interrogation, Dr. Steven H. Miles, a physician at the Center for Bioethics of the University of Minnesota, said he had counted about 70 cases worldwide after World War II in which physicians were punished for participating in torture or related crimes. Most were in Brazil, Argentina, Uruguay and Chile, he said. None have been in the United States.

Dr. Miles said that in recent decades, torture had almost always involved medical professionals, and that to deter future misconduct, the medical role in the C.I.A. program should be fully disclosed.