The authorities on Sunday detected twice the number of hot spots in Sumatra, raising fears that the haze is about to surface again.
In Singapore, the Pollutant Standards Index (PSI) - a measure of air quality - crept up into the moderate range for the first time this month, hitting 51.
Singapore's National Environment Agency last week issued an update that brief periods of slightly hazy conditions could be expected over this fortnight.
Residents in Malaysia's Klang Valley also encountered some relief from the haze when it rained on Sunday morning, and by 5pm, only Port Klang, Kuala Selangor and Shah Alam had Air Pollutant Index readings in the unhealthy range, at slightly over 100.
The Pekanbaru office of Indonesia's National Meteorological, Climatology and Geophysics Agency told The Straits Times that a total of 163 hot spots were detected throughout Sumatra on Sunday, more than double the 80 on Saturday.
Of the hot spots identified on Sunday, 77, or close to half, were in Riau, which reported just 44 hot spots a day earlier.
Another 22 hot spots were in Aceh, 16 in Jambi, 14 in North Sumatra and 17 in South Sumatra, with the rest spread across four other provinces on the island.
Haze was also reported in Medan and motorists in Pekanbaru had to drive with their headlights on on Sunday, although flights at the airport were not disrupted.
'The haze appears to be getting thicker to a point where people feel irritation in their eyes and visibility is affected, especially in the early morning,' climate analyst Aristya Arditama told local media.
Local officials handed out masks and advised residents to refrain from outdoor activities. They also repeated reminders to farmers to stop burning fields.
Indonesia's Environment Minister Balthasar Kambuaya had, a day earlier, said taskforces on the ground were working with forestry and agriculture officials to detect and snuff out hot spots, and appealing to local communities not to adopt slash-and-burn methods to clear land.
No detailed information on hot spots in Kalimantan was available, but thick haze blanketed Pontianak and parts of West Kalimantan. Satellite images, however, showed 115 hot spots across Borneo, including in Sarawak.
Malaysia's Bernama news agency also reported satellite images showing that the haze carried by south-westerly winds at hot spots in Riau will move to the west coast of Peninsular Malaysia and the Klang Valley.
Malaysia's environment department reminded the public of a ban on open burning in Selangor, Kuala Lumpur and Putrajaya.