Indonesia has arrested executives from seven companies accused of being behind illegal fires causing air pollution in the region.
Correspondents say such arrests are rare, but could result in fines and prison sentences of up to 15 years.
Haze caused by forest fires is an annual problem but this year has been one of the worst in Indonesia.
Indonesia has declared a state of emergency in Riau province, and nearby countries are also affected.
Malaysia and Singapore have seen deteriorating air quality from the haze, which stretches hundreds of kilometres across South East Asia