(CNN) -- Indonesia began cloud-seeding operations over the island of Sumatra on Monday in an attempt to trigger rain to put out fires creating thick blankets of haze over parts of Sumatra and neighboring Singapore and Malaysia.
Sutopo Purwo Nugroho, a spokesman for Indonesia's National Disaster Mitigation Agency (BNPB), said that three Spanish-built CASA 212-200 aircraft were deployed on Friday to Sumatra. The rain-inducing operations will continue in three specific areas for the next 90 days, Sutopo told CNN.
According to the agency, the number of hot spots in South Sumatra in September has reached 1,241. Hundreds more have been detected on the island of Kalimantan, which is Indonesia's side of Borneo island.
South Sumatra has the highest number of hot spots, or areas of high temperatures that could indicate peat or forest fires. Sutopo says ground operations to extinguish the fires are also ongoing. These include spraying, controlled burning, building trenches to limit the spread of the fire and sluices around the burning peat.
Haze from forest and peat fires has been a perennial problem for the region, particularly during the dry months. Slash-and-burn techniques to clear land and droughts have been blamed for the fires in the past. Using uncontrolled fires to clear land is illegal but enforcement has been an issue.
The worst incidence of fires and haze was in 1997 to 1998. The World Wide Fund for Nature estimates nearly 10 million hectares was burned.
The Asian Development Bank put the damages and losses at about US $9 billion for Indonesia and its neighboring countries. The fires also had significant impact on Indonesia's wildlife, including orangutans, tigers and elephants and protected national parks.
CNN's Kathy Quiano-Castro contributed to this report.