A student wearing a face mask looks out from a window of his classroom in Palembang, on Indonesia's Sumatra island September 10, 2015. Indonesia is investigating 10 firms over worsening forest fires that have created a blanket of smog over Southeast Asia, threatening them with sanctions if they are found responsible, a government minister said on Tuesday. The thick haze from Indonesia's Sumatra and Kalimantan islands has forced the repeated cancellation of flights in the area and pushed air quality to unhealthy levels in neighbouring Singapore and Malaysia. (Photo by Reuters/Beawiharta)





Students stand on the roof of a wooden boat as haze blankets the Musi River while they travel to school in Palembang, on Indonesia's Sumatra island, September 10, 2015. (Photo by Reuters/Beawiharta)





Students jump from a wooden boat as haze blankets the Musi River while they travel to school in Palembang, on Indonesia's Sumatra island, September 10, 2015. (Photo by Reuters/Beawiharta)





Students, wearing face masks, walk in front of their school as they prepare to head home due to the unhealthy quality of air in Palembang, on Indonesia's Sumatra island, September 10, 2015. (Photo by Reuters/Beawiharta)





Students pay their respects to their teachers as they are dismissed early from school due to the unhealthy quality of air in Palembang, on Indonesia's Sumatra island, September 10, 2015. (Photo by Reuters/Beawiharta)





Students sit on a wooden boat as they head home earlier from school, due to the unhealthy quality of air in Palembang, on Indonesia's Sumatra island, September 10, 2015. (Photo by Reuters/Beawiharta)





An Mi-17 helicopter dumps water on a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An Mi-17 helicopter collects water from a canal to be used on a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An aerial view of a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





A crew member of an Mi-17 helicopter lays on the floor of the chopper as water is dumped on a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An Mi-17 helicopter dumps water on a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An Mi-17 helicopter pilot flies over a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An aerial view of smoking rising from a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An Mi-17 helicopter carries water to be dumped on a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





Indonesian soldiers arrive at Talang Betutu airport in Palembang to reinforce firefighter teams in south Sumatra province September 10, 2015. Indonesian authorities deployed 1,000 soldiers to south Sumatra province to fight land fire in the area. (Photo by Reuters/Beawiharta)





Indonesian soldiers arrive at Talang Betutu airport in Palembang to reinforce firefighter teams in south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An Mi-17 helicopter dumps water on a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





An Mi-17 helicopter dumps water on a burning forest at Ogan Komering Ulu area in Indonesia's south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





Aerial view of housing complex near Musi River as the haze blankets over Palembang, Indonesia's south Sumatra province, September 10, 2015. (Photo by Reuters/Beawiharta)





An Indonesian soldier wearing a mask arrives at Talang Betutu airport in Palembang to reinforce firefighter teams in south Sumatra province September 10, 2015. (Photo by Reuters/Beawiharta)





Students sit in a wooden boat as they head home from school earlier than usual, due to the unhealthy quality of air in Palembang, on Indonesia's Sumatra island, September 10, 2015. (Photo by Reuters/Beawiharta)