An official at Vang Vieng’s tourist police office, who declined to be named, told The Associated Press on Friday that a “number of people” had been arrested in the case but that no charges had yet been filed. Staff at Nana Backpacker Hostel, which was still operating but not accepting new guests, confirmed that the manager and owner were among those taken in for questioning.

Tourist police offices are common in Southeast Asia and are set up specifically to assist with incidents involving tourists and other foreigners.

The US State Department on Friday issued a health alert for citizens traveling in Laos, warning of “suspected methanol poisoning in Vang Vieng, possibly through consumption of methanol-laced alcoholic beverages,” following similar warnings from other countries whose nationals were involved.

Australia’s prime minister announced Thursday that a 19-year-old citizen, Bianca Jones, had died in a Thai hospital where she had been evacuated for emergency treatment, and that her friend – Bowles – remained in hospital “fighting for his life”. A 28-year-old British woman, Simone White, also died of suspected methanol poisoning in Laos, the British Foreign Office said.

An American and two Danish tourists also died, but details of the causes of death have not been released.

New Zealand’s foreign minister said one of its citizens was ill in Laos and was a possible victim of methanol poisoning.

Laos is a communist one-party state with no organized opposition and the government is tight on information. In this case, officials have released almost no details.

The Foreign Ministry has declined 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 city’s health office on the hospital grounds. City health officials declined to comment, saying they lacked the proper permits.

Methanol is sometimes added to mixed drinks at reputable bars as a cheaper alternative to ethanol, but can cause serious poisoning or death. It is also a by-product of poorly distilled home-brewed spirits, and could have found its way into bar drinks by mistake.

Landlocked Laos is one of Southeast Asia’s poorest nations and a popular tourist destination. Vang Vieng is especially popular with backpackers looking for partying and adventure sports.

Neil Farmiloe, a New Zealander who owns the Kiwi Kitchen restaurant in town, said many of his customers were very concerned about the incident.

“I think it’s never happened before, so hopefully it’s just a one-off,” said Farmiloe, who has lived in Vang Vieng for 20 years. “It’s very sad all around. I’m sure no one intended to cause harm, but it has happened.”

The two 19-year-old Australian women, who have both now died, fell ill on November 13 after a night out drinking with a group.

They failed to check out of 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 of “brain swelling due to high levels of methanol in her system.”

Duong Duc Toan, the manager of the Nana Backpacker Hostel, told the AP the day before he was arrested that the two women had joined other guests for free shots of Laotian vodka before heading elsewhere and returning early in the morning.