The mystery deepens over what led an attacker to chew off most of another man’s face as toxicology results are revealed.

1:40am UK, Thursday 28 June 2012
Miami cannibal attack: Rudy Eugene and victim Ronald PoppoPolice at the scene of the attack by Eugene, top left, on Ronald Poppo, 65
Ronald Poppo with medical staff after initial surgery. Source: Jackson Health SystemRonald Poppo survived the grisly attack

Marijuana was the only drug found in the body of a face-chewing attacker shot dead as he ate his homeless victim’s flesh.

Active chemicals from the drug were detected in Rudy Eugene’s system, but there was no sign of illegal or prescription drugs, or alcohol.

The 31-year-old’s girlfriend had previously said he must have been drugged without his knowledge before the attack on 65-year-old Ronald Poppo in Florida.

The results were released weeks after a Miami police union official speculated that Eugene’s bizarre behavior may have meant he was under the influence of “bath salts”, a synthetic stimulant which can cause aggression and hallucinations.

Another woman identifying herself as his girlfriend had suggested he might have been under the influence of a voodoo curse.

It remains unclear what led Eugene – said to be a religious man who read the Bible and the Koran – to take off all his clothes and carry out the grisly assault on Mr Poppo, who was also stripped naked and beaten.

The police officer who shot Eugene dead said he growled when he told him to stop before continuing to eat his victim.

Pictures released of Mr Poppo in hospital in the days after the attack showed the appalling extent of his injuries, with much of the skin on his face stripped away and his nose missing.