Darrel Webber, Secretary-General on the Environmental Pollution in Southeast Asia, identified them as PT Jatim Jaya Perkasa, Tabung Haji Plantations, Sinar Mas, Kuala Lumpur Kepong and Sime Darby.
He said the environmental pollution caused by forest fires in Indonesia that has enveloped several countries in South East Asia to such hazardous levels was deplorable.
He said the RSPO firmly condemns any negligent activities related to this.
"The RSPO is highly concerned about the impact on communities and children living in these countries and strongly advocates urgent measures to be taken to cease this heightening pollution.
"To all those individuals, companies and groups that have provided information and reached out to the RSPO to look into this matter, thank you.
"We assure you that as an international multi-stakeholder organisation and certification scheme for sustainable palm oil, the RSPO's Principles and Criteria explicitly indicate that no open burning is permissible," he said, in a statement.
Within its capacity, the RSPO is critically looking into this to first of all identify the member organizations that have been indicated as well as implicated, he said.
Secondly, he said that RSPO would instruct them to immediately deploy measures to terminate any open burning that may have been caused by them and thirdly, RSPO would take remedial actions against these companies if the fires were due to negligent conduct.
By virtue of being a RSPO member, Webber said, it is a must that these companies have a policy across all their operations that strictly prohibit open burning and have standard operating procedures to manage fire risks as per the requirement of the RSPO's Principles and Criteria.
The RSPO would be directing these member companies to submit digital maps of their plantations in Sumatra and Kalimantan within the next 48 hours. These would be used to assess and analyse against the published mapping of the forest fires by Nasa (National Aeronautics and Space Administration) and NOAA (The National Oceanic and Atmospheric Administration).
The analysis, he said, would assist in confirming the locations of the forest fires in comparison with the location of plantations owned by these member companies, which will then form the basis for the next step in the investigation.
"The next step will focus on validating the reason behind the forest fires on whether this is due to negligent conduct or otherwise. If the investigations confirm negligent conduct, the RSPO will not hesitate to take action," he said.
However, Webber said, the RSPO recommends avoiding speculation at this stage to allow investigations so as to determine whether these RSPO member companies were involved.
It is apparent, he said, based on independent reporting done by the World Resources Institute, that there are several sources to the current fires.
According to him, 47 per cent of the fires in Indonesia originate outside of forest or oil palm plantation while 27 per cent originate in timber plantations, 20 per cent in oil palm plantations, 4 per cent on protected areas and one per cent in logging areas.
While RSPO is a platform for recourse towards its member companies and will do whatever it takes to play its part in reducing the hazardous pollution, he said, it is highly crucial that this is a collective effort.
He said this is because as its member companies make up a diminutive portion in the overall scale of the issue, other regulatory enforcement must immediately and urgently step in.
"The satellite imagery on the forest fires clearly delineate that it is highly prevalent within peatlands," he said.
He said peat systems cover large areas and each system may include multiple landowners and land use.
Fires that begin within peatlands, he said, do not necessarily manifest in the same location as it is often indicated that they spread along great distances underground, invisible to the eye before the fire actually appears.
"This makes it much more important to ensure that the effective management of peat is implemented at a landscape level rather than on a management unit level," he said.
Hence, Webber said, authorities should ensure effective landscape level management protocols are in place prior to allowing any development on peat.
Meanwhile, Tan Sri Dato' Mohd Bakke Salleh, Sime Darby President and Group Chief Executive said the company fully supports the initiative by RSPO.
"I would like to reiterate Sime Darby's commitment and full compliance of the zero burning policy, which is strictly embedded in all our oil palm plantation operations," he said.
Sin Chuan Enga, Kuala Lumpur Kepong Head of Sustainability, the company will be making arrangements to submit the digital maps of its plantations to RSPO and shall give the RSPO fullest cooperation during the process of the proposed investigations.