Scientists are relaunching a $30 million (£18m) study into alternative drugs to treat heart disease despite concerns over its safety.
The controversial research was suspended last August, when the federal office of Human Research Protections investigated whether participants were being fully informed of risks and adequately protected.
Despite the continuing probe, more heart attack survivors are being enrolled on to one of the largest alternative medicine experiments ever launched.
Volunteers are being tested with high doses of vitamin and mineral supplements and chelation, which is used to treat lead poisoning but has not been approved effective for heart disease.
Chelation includes doses of the man-made amino acid disodium EDTA, which it is believed can move the calcium deposits from the artery walls that lead to heart problems.
When the study began in 2002 researchers hoped to enroll 2,400 people across the US, but recruitment levels fell and it is now aiming to test 1,700 people with the drug.
Scientists have argued that participants were not informed that others have died from chelation and doctors running the study have conflicting interests because they make money by selling chelation treatments.
The Office of Human Research Protections said there was merit to the complaint and began an investigation which is still ongoing.
Copyright Press Association 2009