(CNN) The organizers of the Singapore Grand Prix have said the event will go ahead as scheduled despite the haze shrouding the island city-state.
In a statement, Singapore GP said current air quality levels -- rated unhealthy rather than dangerous on the Pollutant Standards Index (PSI) -- meant there were "no plans to amend the published racing and entertainment program."
But with the floodlit night race taking place this weekend, the statement added: "The haze situation is highly changeable, not only from day to day but also from hour to hour.
"Therefore, it is currently not possible to reliably predict what the PSI level might be over the race weekend.
"We will continue to work closely with all the relevant government authorities to receive the best possible forecasts when they are available."
Singapore GP said pollution masks would be sold throughout the Marina Bay street circuit on which the race is held, with all first aid posts "on standby to handle any possible haze-related conditions."
An annual problem, the haze is caused by farmers in neighboring Indonesia burning forests to clear land for farming.
This year it has resulted in some flights being delayed or canceled, but the race authorities have said it could only threaten the event if "visibility, public health or operational issues" developed.
The September 20 race, the 13th round of this year's Grand Prix schedule, costs the Singapore government $65 million a year to host.