The strong burning smell that has hit many areas of Singapore likely comes from fires from across the Causeway or Borneo.
Winds blowing from the north- east and east could be carrying the haze here, said experts, although the National Environment Agency said local vegetation fires could have also played a part.
The 24-hour PSI, a measure of air quality here, continued to hover in the moderate range, and reached a high of 84 in northern Singapore at 8pm yesterday. This is the highest 24-hour PSI reading this year.
Other areas in South-east Asia are also suffering from poorer air quality. Nasa-based satellite imagery on Tuesday and yesterday showed several hot spots raging in Cambodia, Vietnam, northern Thailand, as well as in Myanmar and Laos.
Hunting is adding to the hazard in several parts of Indochina during the hot, dry months from February to April, when farmers burn agricultural waste and clear land by fire.
Dr Nion Sirimongkonlertkun, a lecturer from the Rajamangala University of Technology Lanna, said some fires in northern Thailand have been caused by hunters setting forests alight to expose wildlife.