Five Indonesian provinces have declared states of emergency as peatlands burn in Aceh and the risk of fires spreading elsewhere increases during the annual dry season, an official said Wednesday. National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said 18 helicopters have been deployed to help extinguish fires in Sumatra and Kalimantan. Satellite images show that the number of fires increased from 150 on Sunday to 179 on Tuesday, he said. Nugroho said the provinces of Riau, Jambi, South Sumatra, West Kalimantan and South Kalimantan have declared emergencies in anticipation of a worsening of the fires and to mitigate the choking smoke that peatlands generate when burned. A state of emergency was earlier declared in West Aceh district, where fires on peatland expanded over 70 hectares (170 acres) within a week. Devastating dry-season fires in 2015 burned through 2.6 million hectares (6.4 million acres) and blanketed Sumatra, Borneo, Singapore, Malaysia and southern Thailand in health-damaging haze. Plantation companies and villagers set the illegal fires because it is a faster and, for them, less expensive way to clear land than using machinery. The 2015 disaster, which the World Bank estimated caused $16 billion in losses, was worsened by El Nino drought conditions but also showed the risks that palm oil and pulp wood companies have taken in draining Indonesia's peatlands for use as industrial plantations, making them highly combustible. Yusmadi, chief of Aceh's disaster agency, said at least 23 villagers are being treated at hospitals due to respiratory problems. Nugroho earlier warned that forest and peatland fires would worsen in the coming months, with the peak of the dry season expected in August and September.