A state of emergency was declared for parts of southern Malaysia as airborne pollution spread out of neighboring Indonesia.
Pollution indices soared above the 750 mark, the Australian ABC News website said on Sunday. A reading of 300 implies hazardous air quality. Visibility and air quality was poor again on Monday.
People were urged to state indoors. Some schools and businesses were shut, the BBC News website said.
The cause of the shroud of smoke and haze was the same as what affected Singapore earlier in the week: illegal land-clearing blazes set in neighboring Sumatra, according to the BBC. With pollution levels reaching 16-year highs, Sunday's emergency declaration applied to the state of Johor, which lies next to Singapore.
In Kuala Lumpur, the Malaysia capital, visibility dipped at times to one-half of a mile on Sunday, then fell farther to below one-half of a mile on Monday, meteorological data accessed by AccuWeather.com showed.
Land clearing in Sumatra, Indonesia, is undertaken to replace forest with oil palm plantations. Burning slash and peat after the removal of trees is done to prepare the ground. Although the burning is illegal, enforcement is difficult, according to the BBC.
Authorities in Sumatra were carrying out water drops to fight fires, the BBC. Cloud seeding to trigger rain was also being undertaken.
The burning season in Sumatra coincides with the yearly dry season, lasting from June to September. At this time of year, the South West Monsoon, which gives South Asia the bulk of its yearly rainfall, shifts the focus for rain north of the area of Malaysia.
Meteorological tools available to AccuWeather.com indicated that the fire areas would get scattered daily thunderstorms, much as it would typically in the dry season, through at least the end of the week.
Meanwhile, steering winds over the fire area and Malaysia were forecast to be light and variable, suggesting that the focus of worst pollution could tend to shift, even spreading into new areas.