SINGAPORE, Nov. 1 -- Fine particulate pollution across Singapore returned to normal levels this morning after a brief spike in the west, although fires in neighbouring Indonesia continued to raise concerns over the risk of transboundary haze.

One-hour PM2.5 readings in the western region reached 59 at 5am and 6am, placing them in the elevated band, according to Singapore-based media organisation Channel News Asia (CNA).

By 11am, readings across Singapore's five regions had fallen to between 31 and 46, all within the normal range.

The country's 24-hour Pollutant Standards Index (PSI), which measures overall air quality, stood at between 70 and 88 at 11am, within the moderate range.

Singapore's air quality has remained in the good-to-mo...