At least 83 people died as human guinea pigs in macabre US research on sexually transmitted diseases in Guatemala in the 1940s, a commission ordered by President Barack Obama concluded Monday.

Nearly 5,500 people were subjected to diagnostic testing and more than 1,300 were exposed to venereal diseases by human contact or inoculations in research meant to test the drug penicillin, the presidential commission found.

Within that group, "we believe that there were 83 deaths," said Stephen Hauser a member of the commission, which has pored over 125,000 documents linked to the shocking episode since being set up by Obama last November.

Among the 1,300 people exposed to STDs during research between 1946 and 1948, "under 700 received some form of treatment as best as could be documented," Hauser said.

Obama personally apologized to Guatemalan President Alvaro Colom in October before ordering a thorough review of what happened. Secretary of State Hillary Clinton described the experiments as "clearly unethical."

The Guatemalan president has called the 1946-1948 experiments conducted by the US National Institutes of Health "crimes against humanity" and ordered his own investigation.

Unethical US Research Killed 83 in Guatemala