The government plans to sue three oil palm plantation firms and one oil palm entrepreneur for allegedly starting fires in their concessions that grew into massive forest fires in Riau province.

The State Ministry for the Environment identified the companies Friday as PT Subur Arum Makmur, PT Riau Andalan Sentosa and PT Agro Sarimas Indonesia. The individual is identified as Deden.

"We will file criminal and civil lawsuits. We're compiling their offenses now," said Hoetomo, the state ministry's deputy for environmental law enforcement.

The country's environment, forestry and plantation laws, as well as its criminal code, ban burning land to clear it. The offense carries a maximum penalty of 15 years in prison and billions of rupiah in fines.

The ministry is probing three other companies, including State Plantation V, which manages oil palm, rubber and cacao plantations in Sumatra. It is also investigating two firms in Kalminantan, PT Mitra Aneka Rezeki and PT Wilmar Sambas Plantation, as well as a foreign investment firm referred to only as PT BCP.

"As for BCP, we're currently investigating the owner's country of origin," Hoetomo said.

Masnellyarti Hilman, deputy minister for environmental management, said the government decided to sue the companies because fire "hot spots" had been occurring in their concessions since last year and nothing had been done about it.

She said she believed the legal actions would deter other companies.

"Satellite images show that most of the fires in Sumatra and Kalimantan occur in concessions belonging to logging and plantation firms," she added.

Ministry data shows that from June to August this year, more than 53 percent of the 6,734 hot spots in Sumatra have occurred on the concessions of logging, industrial timber estate and plantation firms. Hot spots are places that produce enough heat to trigger satellite sensors, but not all of them are fires.

More than 65 percent of the 5,705 hot spots in Indonesia's part of Borneo also took place on business properties.

Masnellyarti said the ministry would seek compensation for environmental losses, such as the loss of biodiversity and the degradation of the forests' ability to absorb carbon emissions, which is vital to halting global warming.

Greenomics Indonesia has estimated that forest fires and haze are costing the government, the public and the private sector more than Rp 227 billion (almost US$25 million) a day in deforestation, damage to health and other effects.

State Minister for the Environment Rachmat Witoelar said the lawsuit would aim to prove that the country's rampant forest fires were intentional rather than natural.

"We also want to show that we're not only targeting small-scale farmers or nomadic farmers, but also big players," he said.

The companies' executives could not be reached for comment and are not listed in the country's trade and industry directory, the Sumatra or Borneo yellow pages, or with the province's 108 information operator.

Derom Bangun, the executive chairman of the Indonesian Association of Palm Oil Producers, said these companies might affect the image of the country's oil palm industry, but his organization fully supported the ministry's move to enforce the law.