The tourists in Fiji, who were reportedly staying at a resort on the Coral Coast, were initially taken to Sigatoka Hospital.
They were all later transferred to Lautoka Hospital, according to the Fiji Times.
A 56-year-old Australian woman was under constant surveillance in hospital and a 19-year-old woman, also from Australia, suffered “serious medical episodes”, according to ABC News.
Two other Australian women, aged 49 and 18, were in a critical but less serious condition, the ABC reported.
Tourists have been advised to “be alert to the potential risks around drink spiking and methanol poisoning through consuming alcoholic drinks in Fiji” by Australia’s Department of Foreign Affairs and Trade (DFAT).
The guidance said tourists should “get urgent medical help if you suspect drink spiking”.
Fiji police are said to be investigating the circumstances of the incident.
Two Australian families in Fiji are receiving consular assistance, an Australian foreign ministry spokesperson told the BBC.
