City employees in Thailand’s capital, Bangkok, were ordered Thursday to work from home for two days, and those in the private sector were encouraged to do so as well, as air pollution soared to unhealthy levels.

Air pollution has been a problem for many years in Thailand’s north, where the burning of forests and agricultural waste are major contributing factors. But in recent years Bangkok has also begun to suffer greatly with extended periods of high pollution that have led to school closings and other disruptions.

The Department of Pollution Control declared last month that Bangkok had officially entered its annual smog season, but the region has suffered from deteriorating air quality since late last year. For Chiang Mai and other northern provinces which experience prolonged high levels of microscopic dust, the season usually begins in late February, when dry weather and an atmospheric inversion layer cause airborne particles to accumulate.

Bangkok’s Air Quality Index measured an unhealthy 156 on Thursday, with readings of over 163 in some areas, prompting the stay-at-home order, according to the city government.

High air pollution levels in Thai capital spark order for city employees to work from home | AP News