The National Environment Agency (NEA) said on Saturday that the smoky smell, which covered the eastern part of Singapore, was caused by a Johor landfill fire at Bandar Tenggara that has been burning since Tuesday, February 5.
A spokesperson of NEA told Channel NewsAsia that the "Malaysian authorities have been working around the clock to stop the burning."
The residents of the eastern part alerted the authority about the smoky smell, which started to bother the local Singaporeans since Friday morning. Later, NEA said that the authority did not find any local sources of burning or factory upsets" that could be a reason behind the smell and added that no trans-boundary haze was detected in the region.
On Friday, between 4 am to 5 am the hourly PM2.5 readings in the eastern side were recorded at 70 to 73Âµg/m3, in Band II (Elevated) for air quality. Later, at around 11 am, the air quality improved to Band I (Normal).
NEA said that at around 10 pm on Friday night, they received reports about the return of the smell from residents in the area. However, when the agency checked with Johor's Department of Environment, they confirmed the landfill fire.
"The winds over Singapore have been blowing from the northeast over the past few days and are forecasted to persist for the next few days," NEA added.
The agency said that the hourly PM2.5 readings in that area around 7 am on Saturday ranged from 7 to 34 Âµg/m3, in Band I (Normal). But NEA confirmed that they are "monitoring the air quality and will provide updates should there be any change in the situation."