Rudy Eugene, the man who chewed off most of another man's face in a growling naked frenzy before being shot by police last month, only tested positive for marijuana, the local medical examiner said.
The 31-year-old was initially suspected of being under the influence of "bath salts", a new synthetic drug believed to have caused similar behaviour in others, but the blood test ruled out the most common ingredients.
"The department's toxicology laboratory has identified the active components of marijuana," the Miami-Dade County Medical Examiner said on Wednesday.
"The laboratory has tested for but not detected any other street drugs, alcohol or prescription drugs, or any adulterants found in street drugs."
It said an outside forensic toxicology laboratory had "confirmed the absence of 'bath salts', synthetic marijuana and LSD."
The grisly attack unfolded in the middle of the afternoon near a downtown bridge. When police arrived they found Eugene, naked, growling and gnawing off the face of homeless man Ronald Poppo (65), who was also naked.
Police ordered Eugene to stop and then shot him dead when he refused. The incident, dubbed the "Zombie Attack," made headlines across the country.
Police had suggested Eugene was under the influence of "bath salts," a synthetic stimulant usually sold in shops selling drug paraphernalia which produces intense hallucinations and sparks erratic, violent behavior.
Miami police issued a warning about the drug earlier this month when a snarling homeless man threatened to eat two officers a week after the original incident.