Malaysia's government has ordered 34 schools in southern Johor state to close after toxic waste illegally dumped into a river sickened scores of students and teachers.
Education Minister Maszlee Malek said in a statement Wednesday that the shutdown was necessary because the situation had turned critical.
More than 500 people have reportedly fell ill with symptoms such as breathing difficulties, nausea and vomiting, and treated for chemical poisoning after breathing in toxic fumes from the waste.
Environment Minister Yeo Bee Yin was quoted by the country's Bernama news agency as saying that rain could have caused the contamination to spread despite efforts to contain it.
Three people have been detained during an investigation. Two are factory owners.