Nearly 500 schools and kindergartens in Malaysia have been ordered to close until Thursday after many students complained of breathing difficulties and vomiting.
It's the second such incident this year, where students have been hospitalised with symptoms suggesting they breathed toxic fumes, possibly from waste dumped by factories.
Prime Minister Mahathir Mohamad has vowed to take tough action against those responsible for it.
"It seems like there are factories that are not very concerned about safety and thus, causing the incident to recur," he said. "That is why we have to identify those responsible for causing the pollution and take stern action."
Global airlines race to fix A320 jets after Airbus recall
Death toll in Sri Lanka rises to 153 after Cyclone Ditwah
Hong Kong mourns victims of blaze that killed 128 and counting
Vast Russian overnight attack on Ukraine kills two, wounds dozens
Indonesia flood death toll climbs to 303 amid cyclone devastation
