Videos and images circulating on social media showed villages and highways completely blanketed by an eerie, red-colored haze in the middle of the day through the weekend and earlier this week.
The red skies were caused by a phenomenon called Mie scattering, which occurs when sunlight is scattered by tiny particles in the air, the country's Meteorology, Climatology, and Geophysics Agency (BMKG) explained on Instagram. The scattering happens when the diameter of the particles is similar to the wavelength of visible sunlight, the agency said.
BMKG said at the time of the red haze, satellite imagery showed a high number of hotspots around Jambi with a high concentration of particulate matter PM10.
Particulate matter, or PM, is a type of air pollutant that consists of small particles, from tiny molecular clusters to the dust or pollen that we can see. PM10 is particulate matter with a diameter of 10 micrometers or less.
Speaking to CNN affiliate CNN Indonesia, the head of information at Indonesia's disaster management office, Agus Wibowo Soetarno, said the high concentration of smoke and dust posed health risks to residents and urged the public to exercise caution when driving in low visibility.
According to Air Quality Index (AQI) monitoring site AQICN, Jambi province reached "hazardous" levels over the weekend, which signaled that residents may experience "serious health effects."
'State of emergency'
Neighboring Riau province declared a state of emergency Monday as air pollution continued to worsen, according to Antara media agency. Some residents have been forced to evacuate to other cities because of the hazardous air quality.
The smog has also impacted neighboring countries, including Malaysia and Singapore.
The Malaysian government has distributed some two million face masks to students in affected areas, according to national news agency Bernama. Some 600 schools were also temporarily closed in the country due to unhealthy levels of air pollution.
Indonesian police said that the majority of forest fires were caused by human factors. According to police spokesman Dedi Prasetyo, close to 200 people have been arrested over their alleged involvement in the blaze, which have burnt some 328,000 hectares of land.
Fires and smog are a persistent problem during the summer months caused by slash and burn techniques to clear the land for agricultural purposes. For around two decades, large paper and palm oil plantations have farmed the rich peatlands that run along the Sumatran coast of Indonesia and the island of Borneo.
Authorities in Indonesia have long tried to put a stop to the illegal practice, and those found guilty can be fined up to 10 billion rupiah ($700,000), while managers of firms doing the burning can face up to 10 years in jail. Despite this however, the fires have continued.
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