Four westerners were among at least 24 people killed by toxic alcoholic drinks on the tourist islands of Bali and Lombok in the past week, prompting urgent warnings to visitors to steer clear of homemade brews. Sugianyar, a spokesman for the police in Bali, said autopsies conducted on some of the victims confirmed the cause of death to be poisoning from methanol, a toxic form of alcohol commonly used as lamp fuel. Ingesting even a small quantity can cause blindness and death. In Bali, methanol is sometimes mixed with the locally brewed arak, a liquor normally distilled from fermented fruit, grain, sugarcane or coconut palms. Among the victims were Dutch tourist Rene Puper, 23, who died in a Lombok hospital on Sunday night, a day after his British girlfriend, Rachel Craig, 22, passed away on the nearby island of Gili Trawangan. In Bali, 59-year-old Briton Alan Colen, a resident of the Canggu region married to a local woman, also died on Sunday, while American artist Rose Johnson, 48, a long-time resident of the sleepy village of Sanur, died on Monday at Denpasar's Sanglah Central Hospital. Spiked arak is often produced by home breweries and is popular among the less affluent youth of the islands. 'We have already found one illegal brewery and arrested two people,' said Mr Sugianyar, who like most Indonesians has only one name. 'But it is quite likely that there are more. We cannot be sure how much spiked arak is still out there. The advice to tourists and residents alike is to stay away from unknown brands of arak,' he said. The rest of the victims are Indonesian, and all of them died in Bali. Putu Putra Wisada, head of public relations at Sanglah hospital, said it had already received 48 people thought to have been poisoned by methanol. 'The first patient was admitted on May 26. A further 24 are still undergoing treatment,' he said. 'They have all shown the same symptoms, including loss of consciousness, blurred vision, nausea and vomiting. Those victims in the most serious condition have also suffered acute kidney failure,' he added. Several more people have been admitted to a hospital in Tabanan, a district in the west of the island. Spiked alcohol is a widespread problem in Indonesia, a country of 240 million people where controls on breweries are lax and a growing alcoholism problem is hidden by a lack of data. In January, 14 people died in Central Java after drinking a concoction of 90 per cent alcohol mixed with ginseng, vanilla extract and fermented tea. In September, 12 people died in West Java after drinking home-made alcohol allegedly mixed with methylated spirits and insecticide. Last July, at least 14 workers, most of them Thai citizens, died of suspected alcohol poisoning after drinking at a party in Indonesia's eastern province of Papua.