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An aerial picture made available on 20 June 2013 shows smoke raise from burning areas near agricultural plantations in Rokan Hilir, Riau province, Indonesia, 17 June 2013. Indonesian authorities urged residents in Riau province on Sumatra island to stay indoors as haze from forest fires reached unhealthy levels. While a pollutant index reading above 200 is considered very unhealthy, the standard index shot to 293 in Dumai district on 19 June and cases of respiratory infections had been on the rise, health authorities said. EPA/STRINGER

Where Singapore haze is coming from

Heavy smog from fires in Indonesia continued to blanket Singapore Friday, with officials warning that it may linger for weeks or even longer.

The haze, which is said to have driven air quality in the Southeast Asian city-state to "hazardous levels," comes from illegal burning of agricultural lands in Indonesia's Sumatra to clear the way for palm plantations.

Fearing adverse impacts on business and tourism, Singapore has sent officials to a  meeting in Indonesia to urge "definitive action."