Singapore city skyline
File photo Image Credit: AP

Singapore's air quality reached what the government considers "unhealthy" levels, as authorities warned that hazy conditions may be widespread due to forest fires in Sumatra and Kalimantan of Indonesia.

Singapore's 24-hour PSI air pollution reading in the east of the island was as high as 111, according to the National Environment Agency website on Saturday. An index reading between 101 and 200 is deemed "unhealthy," while a level above 300 is categorized as "hazardous."

Smoke from fires in southern Sumatra and Kalimantan reached Malaysia, shrouding some areas of the country and causing air quality to drop, the nation's Department of Environment said on Sept. 30. Indonesia has denied that it is the source of the haze.

Haze from fires is a recurring problem in Southeast Asia, disrupting tourism and costing local economies billions of dollars. It usually originates from natural or man-made fires in Indonesia and Malaysia, such as when conditions are dry and lands are cleared for plantation crops.