Nineteen-year-old Australians Bianca Jones and Holly Bowles died in Thai hospitals on Thursday and Friday respectively of suspected methanol poisoning after drinking tainted alcohol in Laos.
The teenagers had been evacuated from Laos to Thailand for emergency treatment.
Australian teens Holly Bowles and Bianca Jones died in hospitals in Thailand. (HANDOUT/7NEWS)
Both were found sick in their room at the Nana Backpacker Hostel on November 13 after they failed to check out as planned.
The UK Foreign Office named 28-year-old British woman Simone White as another of the victims.
An American man and two Danes also died, although their exact causes of death have not been released.
A New Zealander has also fallen ill.
In a short statement released to the media on Saturday, the Laotian government said it was "profoundly saddened over the loss of lives of foreign tourists" in the town Vang Vieng and offered its condolences to the families of the victims.
"The government of the Lao PDR has been conducting investigations to find causes of the incident and to bring the perpetrators to justice in accordance with the law," it said.
Laos is a one-party communist state with no organised opposition and the government keeps a tight lid on information.
In this case, officials have released almost no details.
Landlocked Laos is one of Southeast Asia's poorest nations and a popular tourist destination. (AP PHOTO)
The police have said they had detained a number of people but refused to provide further information.
Details have been murky over the number of tourists affected and the possible source of the methanol-laced drinks.
Methanol is sometimes added to mixed drinks at disreputable bars as a cheaper alternative to ethanol but can cause severe poisoning or death.
It is also a by-product of poorly distilled home-brew liquor, and could inadvertently have found its way into bar drinks.
The US State Department on Friday issued a health alert for citizens travelling in Laos, warning of "suspected methanol poisoning in Vang Vieng, possibly through the consumption of methanol-laced alcoholic drinks", following similar alerts from other countries whose citizens were involved.
Landlocked Laos is one of Southeast Asia's poorest nations and a popular tourist destination.
Vang Vieng is particularly popular among backpackers seeking partying and adventure sports.
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