A mass drug overdose at a Festival Hall rave could have proved lethal if partygoers hadn't received medical help as quickly as they did, an Ambulance Victoria official says.

Nine people were taken to hospital, some of them in a critical condition, after being treated for suspected drug overdoses at the I Am Hardstyle event at the West Melbourne venue on Friday night. Several others affected made their own way to hospital.

"They are certainly lucky they didn't die on the spot," Ambulance Victoria state health commander Paul Holman said.

Ambulance Victoria commander Paul Holman briefing the media on Saturday about Friday night's drug overdoses.

"They had St John Ambulance there providing first aid, they had a doctor there who was providing intervention.