U.S. Secretary of State Hillary Clinton, seen earlier this week, apologized to Guatemala about U.S. government researchers using prostitutes to deliberately infect prison inmates in Guatemala with syphilis in the 1940s. (J. Scott Applewhite/Associated Press)

The U.S. government has apologized for experiments in which government researchers used prostitutes to deliberately infect prison inmates in Guatemala with syphilis.

U.S. Secretary of State Hillary Clinton and Health and Human Services Secretary Kathleen Sebelius issued a joint statement Friday on the 1946-48 study they called unethical.

"Although these events occurred more than 64 years ago, we are outraged that such reprehensible research could have occurred under the guise of public health. We deeply regret that it happened, and we apologize to all the individuals who were affected by such abhorrent research practices."

Medical historian Susan Reverby of Wellesley College in Massachusetts uncovered the experiment. It apparently was conducted to test the effectiveness of penicillin, which was relatively new then, in treating sexually transmitted diseases.

"In addition to the penitentiary, the studies took place in an insane asylum and an army barracks," Reverby said in a release.

"In total, 696 men and women were exposed to the disease and then offered penicillin. The studies went on until 1948 and the records suggest that despite intentions not everyone was probably cured."

The researchers induced the disease by allowing inmates in the central penitentiary to have sex with infected prostitutes [which was legal in Guatemala], or gave the disease to the prisoners by inoculating their arms, faces or penises with a solution of the bacteria that causes syphilis.

Researchers are organizing a case review to see if people involved in the study, and their contacts, are still alive. If so, they may have passed on the disease.

Current regulations for U.S.-funded human medical research prohibit these kinds of "appalling violations," the government statement said.

With files from The Associated Press