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.

An American is among at least five tourists who have died after visiting a town in Laos where concerns have arisen about alcohol tainted with methanol.

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.