WASHINGTON – A prominent physicians group is charging that medical personnel were used to test and refine the effectiveness of waterboarding and other harsh interrogation techniques for terror detainees in U.S. custody under the guise of safeguarding their health.

Physicians for Human Rights outlined the allegations stemming from a Bush-era interrogation program and called on the White House to investigate. Its report was based on a re-examination and new interpretation of previously released records.

U.S. government officials denounced the report, saying the government did not conduct human research on detainees. The officials said that such charges and documents have already been made public and examined by multiple government probes.

The report’s author, Nathaniel Raymond, said the declassified documents had never been examined with an eye on laws including the Nuremberg Code, established to ban Nazi Germany medical experimentation.

“We’re not writing the indictment here,” Raymond said before the report’s release at midnight Sunday. “We’re seeing there needs to be a search warrant. If the White House does not act on this, it’s turning its back on something that could be perceived as a war crime.”

According to the report, “Medical personnel were required to monitor all waterboarding practices and collect detailed medical information that was used to design, develop and deploy subsequent waterboarding procedures.”

For example, the report said, doctors recommended adding salt to the water used for waterboarding, so the patient wouldn’t experience “a condition of low sodium levels in the blood caused by free water intoxication.”

The report also said information was gathered on the pain inflicted when various techniques were used in combination. Raymond said the purpose was to see if the pain caused violated Bush administration definitions of torture, rather than as a safeguard of the detainees’ health.

CIA spokesman Paul Gimigliano rejected the claims.

The report also questioned the Obama administration’s new high-value detainee investigation group, known as the HIG. Part of its role is to research new interrogation methods. The physicians group demanded clarification, asking whether this meant learning by doing.

Wendy Morigi, spokeswoman for the national intelligence director, said this part of the HIG would look at “scientific research that would allow for a refinement of current best practices” and was “in no way was suggesting research on the detainees themselves.”