"It seems that (the fires) also involved foreign firms," he said in the State Palace compounds in Jakarta on Friday.
He said investigation is still underway to prove the alleged involvement of eight companies in the forest and woodland fires.
But he stopped short of revealing the companies.
"Let us wait and see," he said.
Earlier, Foreign Minister Marty Natalegawa said the government has made an optimum effort to prevent forest fire-induced haze from spreading to neighboring Singapore.
Marty said the Indonesian government has coordinated with the Singapore government to resolve the problem.
To resolve the problem the governments of the two countries have formed a technical forum involving relevant ministries to overcome the haze, he said.
Marty said on Wednesday that the Singapore government had conveyed its concern over fires in Sumatra that had caused haze in the neighboring country.
On Thursday, President Susilo Bambang Yudhoyono ordered all ministries and relevant institutions to put out the forest and woodland fires in one month.
"The President has given us directives that hotspots and haze in Sumatra should be overcome immediately," Chief Economic Minister Hatta Rajasa told a press conference after a cabinet ministers` plenary meeting on Thursday.
Reporting by M. Arif Iskandar and GNC Aryani