Indonesian President Susilo Bambang Yudhoyono left Saturday for Sumatra, to take the lead in an operation to combat massive forest fires, which has so far proved fruitless. The two-week emergency status over the fires, which are still ripping through vast tracts of forest, was extended Wednesday as water-bombing proved futile against the flames. Yudhoyono this week criticised the response led by officials in the province and said Friday he would take control of the response. "I want the regional officials in Riau to stand on the frontline to prevent and handle this haze. Why is it still happening? The people have become victims," he wrote, adding "the results are unsatisfactory". A report by the Washington-based World Resources Institute this week said the current fires were cloaking areas in thick smog. It said the situation was the worst on Sumatra since blazes in June last year, when the choking haze reached as far as Singapore and Malaysia. Air pollution in some parts of Riau province have hit "dangerous" levels in recent days, with 50,000 people receiving treatment for respiratory illnesses, the national disaster agency said, while schools and some businesses have been forced to close. The response had involved more than 800 personnel and 10 aircraft, while Jakarta sent an additional 2,500 people on Saturday to reinforce the effort. Like Sumatra, Malaysia has been experiencing weeks of drought, with haze levels in some parts reaching hazardous levels on Friday, according to the Department of Environment's website. But Malaysia showed a drop in pollutant levels Saturday, and light rains had begun to fall in Riau late Saturday, according to disaster agency spokesman Sutopo Purwo Nugroho, who confirmed the team had been cloud-seeding all week. The World Resources Institute report said "clearing land for agriculture was the major direct cause of the fires" It said that paper giants Asia Pulp & Paper (APP) and Asia Pacific Resources International Limited (APRIL) had significant fires in their concession areas, based on images by Global Forest Watch, a website that can track fires in near real time. APP, which has no-burn and zero-deforestation policies in place, did not confirm that fires were burning in its concession areas, but said: "We do not practice and highly condemn slash and burn activity for its detrimental impact on the environment". APRIL could not be immediately contacted. Forest fires on Sumatra are an annual problem, but are more common during the dry season later in the year.