Jakarta: Indonesia has launched a criminal investigation into the burning of a peatland forest on Sumatra island that environmentalists said resulted in the deaths of orangutans, an official said Tuesday.

Investigators would summon officials from two companies suspected of burning a large swath of the Tripa forest to make way for palm oil plantations, said Sudaryono, the head of law enforcement at the Environment Ministry, who like many Indonesians uses only one name.

"Our investigators found that there have been fires in areas controlled by SPS2 and KA," he said, referring to palm oil companies PT Surya Panen Subur 2 and PT Kallista Alam.

A coalition of local and international conservation groups warned in March that orangutans in the Tripa forest could disappear by the end of this year unless action was taken to stop fires and land clearing there.

The coalition said an estimated 100 orangutans had died in the area in recent years as a result of land clearing, with only 200 remaining.

The government's task force for the UN's Reducing Emissions from Deforestation and Degradation (REDD) programme said there were indications that plantation companies cleared more than 1,600 hectares of peatland areas even before they obtained concession permits.

"Law enforcers concluded that there have been legal violations," task force chief Kuntoro Mangkusubroto said.

Under Indonesia's environmental law, forest clearing using fires is punishable by up to 10 years in prison and a fine of up to 10 billion rupiah (1.08 million dollars).

Kallista Alam has denied wrongdoing and blamed local farmers for the fires.

In May 2011, President Susilo Bambang Yudhoyono signed a decree committing Indonesia to a two-year moratorium on new clearing permits for an area of around 60 million hectares of virgin forest and carbon-rich peatland.

The move was part of the country's commitment to the REDD program, which aims to reduce climate change from greenhouse gasses.

But in August, the then-governor of Aceh province, Irwandi Yusuf, signed a permit to allow PT Kallista Alam to operate in Tripa.

The environmental coalition is awaiting a verdict on an appeal seeking the revocation of the permit.

Tripa was included in the moratorium map in April 2011, but it disappeared from a revised version in November, the local environmental group Walhi said.

Greenpeace said in a report released this month that the moratorium had done little to protect forests, with almost 50 per cent of the country's primary forests and peatland without any protection.

The destruction of peatlands releases large amounts of carbon dioxide that contributes to climate change.

Indonesia is among the largest producers of greenhouse gasses, largely owing to the rapid destruction of its forests. It aims to reduce the emissions by at least 26 per cent by 2020. AFP