Singapore's pollution index climbed back to "hazardous" levels and air quality deteriorated in the Malaysian capital on Saturday as Indonesia came under heavy pressure to bring fires from slash-and-burn land clearing under control.
Indonesia has deployed military planes to fight the blazes on Sumatra island from illegal burning that typically takes place in the June to September dry season to clear space for palm oil plantations. The fires are unusually widespread this year and the smog is the heaviest in Singapore's history.
Companies behind the fires would find no refuge in Singapore, Foreign Affairs Minister K. Shanmugam said on Saturday, even as he acknowledged limits in international law to deal with firms that operate outside the city-state.
"We will do everything we can," he told a news conference.
Indonesia blamed eight companies for the fires on Friday, including Jakarta-based PT Sinar Mas Agro Resources and Technology (SMART) and Asia Pacific Resources International (APRIL).
The Indonesian government, which said it would take action against anyone responsible for the disaster, is expected to name the rest of the companies on Saturday.
Singapore has warned the "haze" - which has fuelled fears about health problems and raised diplomatic tension in Singapore, Malaysia and Indonesia - could last for weeks, or even longer.
On the sixth day of the thick smoke, Singapore's pollution index returned to the "hazardous" zone with readings above 300. It hit a record of 401 on Friday afternoon, a level considered potentially life-threatening for the ill and the elderly.
The smell of burned wood filled the air and visibility was poor, with buildings shrouded in a grey gauze. Streets in the clean and green city-state, which usually enjoys clear skies, were far less crowded than on a typical Saturday when people go out to shop, meet in outdoor cafes and have fun at the park.
The Ministry of Education advised public schools to cancel all activities planned for the holiday month of June.
StarHub Ltd, a cable television and Internet provider, said it was providing a free preview of more than 170 channels over the weekend "as we stay home to escape the unbearable haze".
The cost of the smog for Singapore, a major financial centre and tourist destination, could end up being hundreds of millions of dollars, brokerage CLSA said in a report.
In Malaysia, the haze spread north. Air quality in Kuala Lumpur, the capital, and in several surrounding areas worsened into the "unhealthy" zone. The air quality was now "unhealthy" in 17 areas of Malaysia and "very unhealthy" in one area.
Hadi Daryanto, the general secretary of Indonesia's Forestry Ministry, said a team led by Forestry Minister Zulkifli Hasan was now in Riau province on Sumatra "to find out the exact locations of the hotspots".
"But we have to be very careful in any legal action," he said. "We have to really find out what happened, why the fires happened and so on. This could be due to negligence, too."
"FINE WORDS ONLY GO SO FAR"
Indonesia has earmarked around 200 billion rupiah ($20 million) to handle the disaster. Seven military aircraft were deployed for water bombings and cloud seeding.
"The majority of hotspots in Riau are inside APRIL and Sinar Mas concessions," senior presidential aide Kuntoro Mangkusubroto told Reuters on Friday.
An APRIL statement said it and third-party suppliers had a "strict no-burn policy" for all concessions in Indonesia.
An analysis of satellite maps and government data by Reuters and the think-tank World Resources Institute also revealed spot fires on land licensed to Singapore-listed First Resources Ltd and Indonesia's Provident Agro. The analysis did not reveal the cause of the fires or who was at fault.
A spokeswoman for Golden Agri Resources, SMART's Singapore-listed parent, said it knew of no hotspots on its concessions.
Despite the "zero burning" policies, the environmental group Greenpeace said many producers and traders drive deforestation and destruction of peatland by buying palm oil from third-party suppliers or on the open market.
"Fine words only go so far but can these companies guarantee that they are not laundering dirty palm oil on to international markets?" Greenpeace said in a statement.
"The lack of government transparency makes it very hard for independent monitoring: concession maps are incomplete, data is lacking and we clearly have weak enforcement of laws."