Ambulances were called to the house in Colombo St in Victoria Park shortly before midnight and found seven men and two women in various unconscious or semi-conscious states with some violently ill.
All were hospitalised, with four in intensive care including three men in a critical condition.
Their condition is believed to be drug-related, paramedics were told the people might have taken cocaine or a similar drug and detectives from the organised crime squad are investigating.
Neighbours were woken when nine ambulances and about 20 paramedics turned up in the street and there were chaotic scenes as the people, who are all believed to be aged in their 20s, were wheeled out on stretchers.
Neighbours described a scary scene in which the young people, with "glassy eyes" and one man behaving aggressively.
The house appears to be used as short-term accommodation for backpackers, with locals also describing a hive of activity and constantly changing residents.
