A backpacker who snorted a synthetic drug that sent nine people to hospital in a mass overdose says it felt like his face was 'melting off'.

Three of the tourists returned to the Perth share house on Wednesday, one in a hospital gown and another shirtless and still wearing his ECG electrodes.

The nine who overdosed were only saved from death when two others who didn't take it called triple-0 and they were rushed to hospital on Tuesday night.

Scroll down for video

A backpacker involved a suspected mass drug overdose has returned home (pictured) with a smile on his face, despite having three of his friends fighting for their lives in hospital

A total of nine people were found unconscious at a home in Perth about midnight on Tuesday. When paramedics arrived at the home members of the group were 'rolling around' on the floor

The drug was on Thursday identified as motion sickness drug hyoscine, which is also used as a date rape drug as it puts victims into a 'zombie-like' state.

One of the backpackers said he was 'trying to scream for help' but his mouth wouldn't move throughout the 'terrifying' ordeal.

The young man said he thought the white powder sent to the house from New York by mistake was cocaine.

He was one of five French citizens, aged between 21 and 24, two Germans, aged 21 and 22, an Italian, 25, and a Moroccan, 24, released from hospital on Wednesday.

Two Frenchmen were still fighting for life in Royal Perth Hospital and a German woman was in an induced coma in Sir Charles Gairdner Hospital.

The unknown drug, which was sent for testing, was addressed to someone who never lived at the house, apparently by mistake.

It had a pamphlet inside with the word 'scoop' printed across it and a piece of paper glued down with a lightning bolt symbol, according to Seven News.

It's understood the nine victims, two women and seven men, are all aged in their 20s and are believed to be foreigners currently backpacking or studying in Australia

Ambulance officers who attended the scene told of their shock at finding the group in a zombie-like state, 'rolling around' on the ground of the home when they arrived.

Paramedics had to sedate all nine people at the home due to them 'punched' and 'kicking' at emergency services as they tried to help.

Doctors said the victims would have died if ambulances hadn't been immediately called.

Royal Perth Hospital clinical toxicologist Jessamine Soderstrom said overheating bodies were eventually fatal.

'You go into multi-organ failure and patients die from that,' she told reporters.

'If it wasn't for the timely call of the resident, some of those patients inevitably would have died.'

Emergency services were called to the home in Perth just before midnight on Tuesday, finding a group of seriously ill people in different states of unconsciousness

Royal Perth Hospital emergency doctor David McCutcheon said the patients arrived hallucinating, ill and in a state of agitated delirium and, most seriously, had racing hearts and overheating bodies.

'Several of them have had to be put in a medically induced coma,' he said.

'I need to emphasise how seriously unwell they are. It was lucky there was someone on scene who could call an ambulance, because their lives were in danger.

'It appears the patients didn't know where they were, they were rolling around on stretchers and at the scene as well.'

Dr McCutcheon said doctors were yet to determine exactly what drug the group had allegedly taken, but said their symptoms were common with many substances.

'We don't know the drug involved at this stage so we don't really want to speculate any further at this point,' he said.

Doctors have not yet determined which drug the group had taken, but said they were acting as though they didn't know where they were when paramedics arrived

The house also has a large pool in the backyard

That cluster of systems is quite common to a lot of illicit drugs. There are many synthetic drugs now... and we don't really know much about them.'

Neighbours who watched on as the group was helped from the house described the chaotic scenes as 'really, really scary.'

'They were all coming past in a line, it was so scary and they had glassed eyes and they were like in a different world, it was so scary to look at… a lot of them were having seizures,' Sophie Barnet told the ABC.

'There was one guy that was really violent on the stretcher, he was like punching the air and everything.'

A neighbour told the ABC the house was like a backpackers 'bed and breaskast'

The large wood-finished home has five bedrooms, three bathrooms and a battle-axe driveway that leads to off-street parking

Another local resident described the house as a backpacker's 'bed and breakfast', and said the victims were acting in an almost zombie-like state.

'It was just absolutely crazy. People just started coming out in stretchers, most of them were in like an unconscious state, but one of them was kicking and having almost like a spasm.'

Police seized substances from the home and Organised Crime were notified of the presence of drugs.

The large wood-finished home has five bedrooms, three bathrooms, a battle-axe driveway that leads to off-street parking, and a large pool in the backyard.