Several tourists who died in Vang Vieng, Laos are believed to have drunk tainted alcohol.
An American, two Danes, two Australians, and a Brit died after apparently consuming bootleg liquor that contained methanol, according to multiple reports.
Methanol is sometimes illegally added to drinks because it is a cheap way of increasing alcohol content. However, even a tiny amount can be lethal.
On Friday, the family of 19-year-old Australian tourist Holly Bowles confirmed she had died in a hospital in Thailand, a week after she fell ill in Vang Vieng.
Bowles' friend Bianca Jones and British lawyer Simone White from London were also confirmed to have died on Thursday.
Denmark's Ministry of Foreign Affairs told CNN that two Danish nationals had died but provided no further details. An unnamed US man is also believed to be among the victims.
"This is every parent's very worst fear and a nightmare that no one should have to endure," said Australian Prime Minister Anthony Albanese.
The Australian Broadcasting Corporation wrote that local authorities in Laos were investigating the case and trying to ascertain where the tainted alcohol came from.
Duong Duc Toan, the manager of the Nana backpacker hostel, told the Associated Press that the two Australian teenagers had been offered free shots of vodka as a gesture of hospitality. He said no other tourists who drank the shots reported they were sick.
It is unclear how the other four tourists could have come into contact with tainted alcohol.
Toan has now been detained for questioning by police, the BBC reported.
The ingestion of methanol, a flavorless, colorless type of alcohol that is used in cleaning products, adhesives, and paints, can lead to nausea, vomiting, and heart and respiratory failure, per the US Centers for Disease Control and Prevention.
According to Médecins Sans Frontières, Asia has the highest incidence of methanol poisoning in the world, with Indonesia topping the list.
Vang Vieng, a small town in the center of Laos, is a popular stop on the Banana Pancake trail popularized by Western backpackers. It is surrounded by mountains, caves, and rivers.
Representatives of the British Foreign Office, the Danish Ministry of Foreign Affairs, and the embassy of Laos in Singapore didn't respond to requests for comment from Business Insider, sent outside business hours.
November 22, 2.30 a.m. — This story was updated to include comments from the Australian Department of Foreign Affairs and Trade.