One of the risks associated with Ecstasy is the possibility of obtaining adulterated drugs that may be more toxic than MDMA. Some of the reported deaths attributed to Ecstasy may likely caused by other, more dangerous drugs.

Source

Laboratory Pill Analysis Program, DanceSafe. For results visit www.DanceSafe.org. See also: Byard RW et al., Amphetamine derivative fatalities in South Australia -- is "Ecstasy" the culprit?, American Journal of Forensic Medical Pathology, 1998 (Sep) 19(3): 261-5. Also see: C.M. Milroy; J.C. Clark; A.R.W. Forrest, Pathology of deaths associated with "ecstasy" and "eve" misuse, Journal of Clinical Pathology Vol 49 (1996) 149-153.