Worsening air pollution driven by wildfires in Indonesia prompted Malaysia to temporarily shut schools in one of its most populated states, just as a major Formula One race in neighboring Singapore approaches.

Some 200 schools, kindergartens and nurseries in Johor state’s Bahu Pahat district, about 140 kilometers northwest of Singapore, were ordered to close today due to the haze conditions, local media reported. The air quality index in the Malaysian capital of Kuala Lumpur was also in the “very unhealthy” range as of Wednesday morning, ranking the city as the most polluted globally, according to data from IQAir.

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Air quality in three of Singapore’s five regions also ranked as unhealthy on Wednesday, days before the city states’s annual F1 weekend, government data showed.

A spokesperson for Singapore GP Pte Ltd., which organizes the race, said it will work closely with relevant agencies “to assess the situation before making any collective decisions regarding the event” should haze cause visibility, public health or operational issues. An F1 spokesperson said conditions are not at any level of concern.

Swaths of Southeast Asia have been clouded in choking smog in recent weeks as Indonesia battles one of its worst wildfire seasons in years. The uncontrolled blazes stem from the long-running use of slash-and-burn agricultural practices, but fire conditions have been exacerbated by an intensifying El Niño that’s parching the landscape.

Environmental group Greenpeace identified more than 20 palm, pulp and sugar companies, including several with links to Malaysia and Singapore, whose land concessions contained sources of smoke from the fires.

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The number of hotspots last month was the highest since 2015, when a regional haze emergency caused widespread disruptions and diplomatic tensions, according to the Forestry Ministry’s fire-monitoring platform SiPongi.

Last week, organizers of the Kuala Lumpur Standard Chartered Marathon canceled a kids’ race on health concerns, while pressing on with other race categories, including the full and half marathon distances. Still, top finishers of the full marathon clocked times that were slower than recent years. The marathon was canceled in 2015.