Laotian police have detained the manager and owner of a hostel where two teenage Australian tourists stayed who were fatally poisoned by tainted alcohol in a case that appears to have claimed the lives of at least six people.
An officer at Vang Vieng's Tourism Police office, who refused to give his name, told The Associated Press on Friday that a "number of people" had been detained in the case but that no charges have yet been filed.
Staff at the Nana Backpacker Hostel, which was still operating but not accepting new guests, confirmed the manager and owner were among those taken in for questioning.
Bianca Jones and Holly Bowles have died they after becoming ill along in Vang Vieng, Laos. (HANDOUT/7NEWS)
Tourist police offices are common in Southeast Asia and are set up specifically to help with incidents involving tourists and other foreigners.
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.
Australian woman Bianca Jones, 19, died on Thursday in a Bangkok hospital where she had been evacuated for emergency treatment, and the family of her friend Holly Bowles, also 19, said on Friday that she had also died a different Bangkok hospital.
Simone White, a 28-year-old British woman, also died from suspected methanol poisoning in Laos, the British Foreign Office said.
An American and two Danish tourists also died, though specifics about the causes of death have not been released.
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.
The foreign ministry has refused to comment, and in Vang Vieng the small hospital where some of the victims are believed to have been treated initially referred all questions to the town's health office on the hospital grounds.
The town health officials refused to comment, saying they lacked proper permission.
Vang Vieng is particularly popular among backpackers seeking partying and adventure sports. (AP PHOTO)
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 have found its way into bar drinks inadvertently.
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.
It has been more than a week since the two 19-year-old Australian women fell ill on November 13 following a night out drinking with a group.
They failed to check out from the Nana Backpacker Hostel as planned and were found sick in their room and then taken to Thailand for emergency treatment.
Thai authorities confirmed that Jones had died by "brain swelling due to high levels of methanol found in her system".
Duong Duc Toan, the manager of the Nana Backpacker Hostel, told the AP the day before he was detained that the two women had joined other guests for free shots of Laotian vodka on the night in question, before heading elsewhere and returning in the early hours of the morning.
Britain's Foreign Office said 28-year-old Simone White had also died of suspected of methanol poisoning in Laos.
New Zealand's Foreign Ministry said one of its citizens was sickened in Laos and was a possible victim of methanol poisoning.