Forest and plantation fires in Rokan Hilir District, Riau province, have produced haze covering the district over the last three days.
The haze significantly reduced the air quality in the region and the pollutant standard index (PSI) to 100, Surya Arfan, head of the Rokan Hilir environmental impact control agency, said here Tuesday.
"At the number, the air quality is categorized as healthy but only in certain hours like midnight until early morning," he said.
A number of local residents suffer from respiratory problem due to the haze, he said.