Singapore faced its worst pollution crisis in more than a decade, after forest fires in Indonesia caused air quality in the neighbouring city to plunge into the hazardous zone, reaching readings of up to 400 PSI on Friday afternoon. Indonesia has refused to apologise for the haze crisis, insisting instead that its government will do everything it can to tackle the problem. SMU Assistant Professor of Law, Eugene Tan, said such pollution was "a persistent problem" between the two countries, dating back to the 1990s. "The Indonesian authorities' seeming indifference to the haze will only strain bilateral relations," Assistant Prof Tan said, adding that Singapore's hands were tied and it "remained at the mercy of Indonesia". He also said that "Indonesia appears to have taken the view that it is doing all it can, and that it is not for neighbouring countries to say what more ought to be done."