Singapore’s air pollution rose to unhealthy levels today, the National Environment Agency (NEA) said, as winds changed direction and brought in light smoke from forest fires in neighbouring Indonesia, according to Reuters .

Singapore is in the middle of its ‘haze’ season, when smoke from forest clearing in Indonesia traditionally chokes the air, but this year has been practically haze free, despite warnings in May it was going to be worse than 2013's record pollution.

The three-hour Pollution Standards Index broke above 100, the level beyond which the air is considered unhealthy, at 1am and remained above that level into the daylight hours, the government agency said on its website.

The NEA warned yesterday that if the wind blew from the south-west, Singapore could experience occasional haze from fires on Indonesia’s Sumatra island.

The smoke blanketed Singapore last June, pushing the air pollution index to a record 401.

In August, Singapore’s parliament passed a bill proposing fines for companies that cause pollution regardless of whether the companies operate on the island, though it remains to be seen how the law can be enforced.

Meanwhile, media reports today said smoke from forest fires has returned to parts of Indonesia’s Riau province and worsened air quality in neighbouring Singapore, according to dpa .     

Satellite images showed seven hotspots indicating fires, according to Ardi Yusuf, an official at the local Environmental Protection Agency.

The blazes are suspected to have resulted from land clearing by local farmers and plantation owners in recent days, he said.     

“People have started to have problems breathing, even at home,” he said.

Haze from forest fires on Sumatra is an annual hazard that often causes pollution indexes in neighbouring Malaysia and Singapore to reach unhealthy levels.

- Agencies