Holly Bowles, a 19-year-old Australian, became the sixth person to die from the suspected poisoning on Friday.

Her friend and community football club teammate Bianca Jones, also 19, a US man and two Danish women, aged 19 and 20, are also among the victims.

The two Australian victims died after being transferred to a hospital in Bangkok, Thailand, while Ms White was treated in Vientiane, the capital of Laos.

The names of the Danish and American victims have not been released.

New Zealand and Dutch officials have also both said they were monitoring incidents involving nationals.

The New Zealand government told the BBC one of its citizens is suspected to have been poisoned with methanol, and the embassy was providing assistance.

News reports and testimonies suggest the tourists may have consumed alcohol laced with methanol – a deadly substance often found in bootleg alcohol.

Medical specialists say drinking as little as 25 millilitres of methanol can be fatal, but it is sometimes added to drinks because it is cheaper than alcohol.