JAKARTA, Indonesia — Indonesian police on Sunday arrested 72 people suspected of starting some of the recent forest and peatland fires as huge blazes in central and western parts of the country triggered a harmful cloud known as a choking haze.

Indonesia has been battling fires driven by an intensifying El Nino pattern and a prolonged dry season, generating dense smoke that crossed into Malaysia, according to Indonesia’s National Disaster Management Agency, or BNPB.

Fires are a regular problem in the country and often strain relations with neighbors.

Plantation owners and traditional farmers often start fires to clear land for farming, said Mohammad Irhamni, director of special crimes at the National Police’s Criminal Investigation Agency.

The arson suspects were being investigated in connection with 89 forest and land fire cases across five provinces on the island of Borneo and four on Sumatra, Irhamni said.

He said most of the suspects were accused of deliberately burning land to clear areas for plantations at lower cost. Investigators were still tracing financial records to determine whether companies financed or ordered the land clearing, signaling the probe could expand beyond those arrested.

“We will not stop at the perpetrators on the ground,” Irhami said in a news conference Sunday in the capital, Jakarta. “We will determine who benefited from these activities and who was ultimately behind them.”

The suspects face charges that carry penalties ranging from hefty fines to prison terms of up to 15 years, he said.

Indonesian President Prabowo Subianto flew on Saturday to Central Kalimantan province, where more than 7,600 hectares (18,700 acres) have burned, to encourage authorities to get the haze cloud under control.

Prabowo promised government resources required to contain the fires, including helicopters and water pumps, and vowed to hold accountable any companies found to have contributed to the fires.

“I hope we can control this soon,” Prabowo said during the visit. “We have experienced worse forest and land fires in the past, and we were able to overcome them.”

Accompanying the president was Prasetyo Hadi, the head of State Secretariat. He said at least four companies in West Kalimantan province are under investigation for allegedly using fire to clear land. If they are proven to have intentionally set the fires, they could face sanctions, including the revocation of their operating permits, he added.

Smoke from the fires on Sunday blanketed parts of Borneo, the world’s third-largest island shared by Indonesia, Malaysia and Brunei. Indonesia administers about three-quarters of the island, where the country’s Environment Ministry recorded more than 3,700 hot spots on Sunday.

BNPB chief Suharyanto said fire activity had increased in West, Central and South Kalimantan provinces on Borneo, where many blazes worsen due to peatlands, prolonging the dangerous haze in several areas.

Fires that appear “extinguished on the surface may still contain embers underneath, so sufficient rainfall is crucial to rewet the peat and fully suppress the fires,” said Suharyanto, who, like many Indonesians, uses a single name.

The western island of South Sumatra also battled fires, with more than 1,700 hot spots detected on Sunday, causing a choked haze cloud and reducing visibility to only 10 meters (33 feet) in some areas, the ministry said.

Cloud-seeding resumed over Kalimantan on Sunday, with 30 helicopters for water-bombing and aerial patrol missions, and another 22 helicopters covering Sumatra.

Meanwhile, Malaysia has suffered severe smoke from the fires, with its eastern state of Sarawak among the hardest hit. One district recorded “very unhealthy” air quality on Friday, while eight others posted unhealthy readings, prompting the closure of nearly 600 schools and affecting about 200,000 students, the Sarawak government said.