BBC has reported that the Malaysian Government has apparently declared a state of emergency earlier this afternoon, after the API hit unprecedented levels of 531 and 529 in Kuala Selangor and Port Klang respectively.
"Government officials said the state of emergency would extend inland to the entire Klang Valley, covering the country's capital, Kuala Lumpur."
The local media has yet to carry any official declaration from the Government but ChannelNewsAsia has also reported similar news.
Update: The Government has issued an official decree declaring a state of emergency ONLY in Kuala Selangor and Port Klang. All work places are to remain closed indefinitely, except for essential services, food shops and supermarkets. The Prime Minister has stressed that the emergency did not mean a curfew, and the Selangor Government will continue to administer the affected areas.