The haze, caused by illegal forest clearing fires in Indonesia, has created the worst air pollution in Singapore since 2006, and led to league leaders Etoile's match with Young Lions and Balestier Khalsa's clash with Geylang both being called off on Thursday.
"Taking into consideration that we are in the first few days of the haze and it has moved into an unhealthy range, FAS decided to postpone both matches as a precautionary measure for our players," league spokesman Isaac Christian said.
Etoile remain top of the table on 64 points, one ahead of Tampines Rovers and Home United, and are now scheduled to play their match on Saturday if air quality is deemed safe.
Etoile coach Patrick Vallee said the postponement would not affect his team's preparations for upcoming matches. Etoile play Bangkok Glass in the RHB Singapore Cup next Friday and their final S-League match will take place in early November.
"What can I do? I can't be angry, I can't do anything. But for my team, the delay is okay," he told the Straits Times.
ASEAN countries have been trying to solve the haze problem since the region was hit severely by smoke pollution in 1997.
"The suspicion is that this is coming from forests that have been opened up for plantations. We think it may be for palm oil," Purwasto Saroprayogi, head of the land and forest fires department at Indonesia's Environment Ministry, told Reuters.
Indonesia has a long history of weak forestry law enforcement and illegal land clearing by palm oil developers is not uncommon.
