SINGAPORE, Sept. 6 -- Air quality across Singapore improved to moderate levels this morning after haze pushed pollution into the unhealthy range in three regions a day earlier, although authorities warned that smoke from fires in Indonesia could continue to affect the city-state.

As of 7am today, all five regions were recording 24-hour Pollutant Standards Index (PSI) readings within the moderate range, according to the National Environment Agency (NEA), CNA reported.

The central region had fallen to a PSI of 91 by midnight, after peaking at 123 at 1am yesterday. The west and east also returned to moderate levels, recording readings of 86 and 77 respectively at midnight.

Earlier yesterday, both regions had crossed into the unhealthy ran...