The U.S., Australia and U.K. have issued warnings for travelers in Vang Vieng after several tourists died in a suspected methanol poisoning outbreak.

Simone White was enjoying a holiday with friends in Laos last week when she accepted a free shot from a bar. The 28-year-old British lawyer has now been named as the fifth person to die in a suspected mass methanol poisoning in the backpacking town of Vang Vieng.

The NHS warns that as little as 4ml of methanol can cause hallucinations and blindness. Half an hour to two hours after consuming methanol symptoms include drowsiness, confusion and irritability. Later symptoms include dizziness, vomiting, severe abdominal pain and diarrhoea.