A fire in southern Johor, which was the likely cause of the burning smell reported by Singaporeans earlier this week, has been put out, the National Environment Agency (NEA) said yesterday.

However, a second hot spot was detected in Johor, about 50km to the east and north-east of Singapore, on Tuesday. The smoke plume from the hot spot was blown south-west by the prevailing north-easterly winds, the environment agency said.

The NEA said it received feedback about a burning smell in many parts of Singapore on Tuesday. It added that haze and a burning smell may be expected in Singapore if the fires in Johor continue.

The earlier incident was the result of a hot spot in southern Johor, 30km east of Singapore. Residents had, between Sunday evening and Monday morning, complained of a burning smell.

The Department of Environment (Johor) later informed the NEA that there was a fire in Punggai, near Bandar Penawar, in the vicinity of an oil palm plantation.

The fire was due to the hot weather in parts of Johor.

In an update, NEA said firemen from Bandar Penawar managed to put out the fire after efforts in the past few days and with rain falling on Tuesday. However, around 20 per cent of the surrounding area remains smoky.

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The NEA said that February is normally a dry month for the surrounding region, and extended periods of dry weather can lead to land and vegetation fires.

The Pollutant Standards Index across Singapore ranged from 31 to 52, in the "good" to "moderate" range, as of 8pm yesterday.

The one-hour PM2.5 readings ranged from seven to 21 micrograms per cubic metre, which is in the "normal" range. PM2.5 is the dominant pollutant during haze episodes.

The NEA said yesterday that members of the public can continue with their normal activities.

"We are closely monitoring the air quality and will provide updates on any significant changes to the air quality situation," the agency said.