Official readings reveal that Singapore’s air quality slipped into the poor category on Saturday, as intensified forest fires from neighboring Indonesia pushed smoke to the city-state.

The 24-hour Pollutant Standards Index readings in the eastern and central parts of Singapore were above 100 at 2 p.m. (0600 GMT), levels at which individuals are recommended to minimize prolonged intense outdoor activity.

Transborder haze is a perennial problem in Southeast Asia as regulatory loopholes make it hard for authorities to eliminate Indonesia’s slash-and-burn land clearing practices.

Singapore’s National Environment Agency said 212 hot spots were detected on Indonesia’s nearby Sumatra island on Friday, up from 65 on Thursday and 15 the day before.

A brief shift in the wind direction on Friday afternoon blew some of the lighter haze toward Singapore, worsening the island nation’s in air quality, it said.

The traditional land clearing methods are used almost every year to clear land in Indonesia for palm oil and pulp and paper plantations that public records show are owned both by domestic and foreign or overseas-listed companies.

Indonesia was dousing forest fires with water sprayed from helicopters and inducing rain through cloud-seeding, the environment minister said on Friday, denying that hazardous haze was crossing borders.

Earlier in the week Malaysia urged Indonesia to take action on the fires within Indonesia’s borders as the air quality in Malaysia hit unhealthy levels.

In 2015 and 2019, such fires burned millions of hectares of land in Indonesia and sent haze billowing across several Southeast Asian countries, generating record emissions, scientists have said.

The most severe haze conditions recorded in Singapore were in September 2015, when the 24-hour index exceeded 300 to the hazardous level, prompting school closures.