Pupils ride boat across Musi River under a blanket of smoke in Palembang, South Sumatra, Indonesia, Sept. 17, 2019. Forest fires often occur in Indonesia as growers use fire to clear lands to make room for new plantation. But the fires often rage out of control especially during the dry season. (Photos: Xinhua)

People ride boat across Musi River under a blanket of smoke in Palembang, South Sumatra, Indonesia, Sept. 17, 2019. Thick haze from a forest fire in Indonesia spreading into Malacca Strait, Singapore and Malaysia was detected by a satellite image on Sept. 14, the Indonesian meteorology and geophysics agency said.

Photo taken on Sept.18, 2019 shows a city view of haze shrouded Singapore. Singapore, Indonesia and Malaysia were shrouded in haze recently due to forest fires.

People walk on the street of haze shrouded Singapore, Sept.18, 2019. Singapore, Indonesia and Malaysia were shrouded in haze recently due to forest fires.

Photo taken on Sept.18, 2019 shows a city view of haze shrouded Singapore. Singapore, Indonesia and Malaysia were shrouded in haze recently due to forest fires.

Photo taken on Sept.18, 2019 shows a city view of haze shrouded Singapore. Singapore, Indonesia and Malaysia were shrouded in haze recently due to forest fires.