Indonesia's environmental monitoring agency, Bapadal, has been trying to get hard evidence to nail those responsible for the dangerous levels of haze that has covered the Riau province over the past week. Straits Times Correspondent Marianne Kearney, while in Pekan Baru, followed one attempt to catch the fire starters

Armed with a global positioning system device and cameras, representatives from the Forestry Department, Estate Crops, the police and Bapadal, the environmental monitoring agency, launched a rare investigation into one of the worst offenders – a 12,000-ha palm-oil plantation that has numerous hot spots showing up on the satellite map. From over 1,000 reported hot spots last year, only nine were thoroughly investigated, noted Bapadal.

When we arrived at the plantation, estate manager Gobi denied knowledge of all but one of the 10 hot spots listed on the satellite map. The one fire on his property, he said, had been started by nearby villagers and was reported to the police on Friday last week.

We then set off for one of the hot spots Mr Gobi said he did not know about. Although it is not so far away, getting there took time. Our vehicle struggled with the bumpy peat roads and the last kilometre was accessible only on foot. The hot spot is a series of sporadic fires on the edge of one of the peat canals, spewing strong smoke. Nobody is around to extinguish them.

Mr Gobi said these fires lay outside his boundary, so he was not obliged to extinguish them. But he had tried, he said. However, he added, with fires in peat swamps, "you think they've been extinguished and then they reappear later". He blamed the nearby villagers for starting these fires. According to him, they wanted to start their own palm-oil farms.

Bapadal investigator Setyo Winarso said he would check if this was community-owned or estate-owned land. According to the recently-passed environmental law, Mr Gobi, who possessed proper firefighting equipment, was obliged to help put out the fires.

The fire-investigation team then decided to head into the extremely hazy distance for the largest hot spot on its satellite map. The fires appeared to be quite large. Mr Gobi argued that they had been started by "villagers who are watching guard over our equipment".

In four hours, the team covered only three hot spots and a few kilometres of road with no hard evidence of the fires being started by the palm-oil plantation. However, night travelling on these roads was very difficult so the team decided to return the next morning with the one government-owned four-wheel vehicle that would allow access to the fires.

Mr Gobi insisted that he did not burn down the trees. He said he used a compression method to clear his land, pointing to the cut tree stumps stacked by the roadside. However, Mr Winarso said it was obvious that land cleared two years ago were not cleared only by felling.

First, the large trees were cleared, then the undergrowth was burnt – a far cheaper and quicker method of clearing. If the undergrowth were compressed, the company would have to wait another year while it rotted before they could use the land.

But for this day's investigation, the police and Bapadal would have to return to question local villagers as to who had started the fires and why there were so many fires burning at night.

Officials have also pointed a finger at foreign-owned palm-oil plantations for starting the fires deliberately. Mr Ardi Yusuf of the environmental supervisory agency's forestry division in Sumatra said it had videotapes of fires in the plantations. It was the Bapadal, rather than the police and Forestry Department, which was keen on stopping the burning.

When asked how the Forestry Department and the police prevented companies from resorting to burning, Mr Darminto Sutano, head of Riau's Forestry Department said they had a process to check for fires in the region. But he did not know if the fires reported last week were being fought as he had not received a report from his local forestry offices in a week.