Tourists to the Indonesian island of Bali were warned against drinking the local spirit arak, after at least 25 people died in the past week when a batch was cut with methanol.
Bali's police said 25 people, including a British national, an Irish woman, a Dutch man and a American woman, died of alcohol poisoning after drinking arak containing methanol -- a toxic chemical compound often used as an anti-freeze or in paint.
Another 21 local residents have been treated at Bali's main hospital of Sanglah, police said.
Police have arrested the owner and an employee of a small rice wine factory in Denpasar, the capital of Bali, after finding evidence of arak that contained traces of methanol. They are investigating if this was accidental or deliberate.
This contaminated batch of arak was distributed to shops and roadside stalls in four different districts of Bali, police said.
Gde Sugianyar, Bali police spokesman advised Balinese and tourists to avoid unlabelled drinks as a precaution.
"We have been watching and conducting raids across Bali especially arak sellers who sell their liquor from jerry cans. We asked Balinese to stop buying unlabelled arak until we find what exactly caused the deaths," Sugianyar told Reuters.
Arak, a colorless, sugarless drink, is distilled from palm sap or rice and commonly used in religious ceremonies in Bali.
It is also much cheaper than imported alcohol, which is heavily taxed. Arak has a high alcohol content of 20 to 50 per cent, making it the drink of choice for some tourists who use it for cocktails to get a so-called "arak attack."
"Tourists do not need to worry as long as they drink labeled alcohol," Sugianyar said.
Police are investigating whether the contaminated Balinese arak was distributed to neighboring islands in West Nusa Tenggara, causing the death of two foreign tourists there, Sugianyar said.
Police said Dutch national Rene Puper, 23, died on Sunday in a Lombok hospital after his Irish girlfriend, Rachel Maria Craig, 25, died on the resort island of Gili Trawangan a day earlier.
In Bali's Sanur district, American Rose Johnson, 48, formerly of Phoenix, Arizona, died on Monday after drinking adulterated arak, while Briton Alan Colen, 59, who lived in Bali for about six years, died on Saturday after consuming what appeared to be some of the same batch of arak.