Heart attack survivors are again being enrolled in a large, controversial federal study of an alternative medicine while the government investigates whether they were told enough about possible health risks.

The study tests high doses of vitamin and mineral supplements and chelation, in this case disodium EDTA, which isn’t totally safe, and carries a risk of kidney failure, bone marrow problems, heart rhythm problems and breathing troubles and so on.

Most sites resumed enrollment in January, and the investigation is still ongoing, even though the study leader and other researchers voluntarily suspended enrollment last August, and some scientists said that the study’s consent form does not tell participants that others have died from chelation.